Related | American Society of Hematology 2018 guidelines for management of venous thromboembolism: heparin-induced thrombocytopenia
CLINICAL GUIDELINES
American Society of Hematology 2018 guidelines for management of
venous thromboembolism: heparin-induced thrombocytopenia
Adam Cuker,1,2 Gowthami M. Arepally,3 Beng H. Chong,4 Douglas B. Cines,1,2 Andreas Greinacher,5 Yves Gruel,6 Lori A. Linkins,7
Stephen B. Rodner,8 Sixten Selleng,9 Theodore E. Warkentin,7,10 Ashleigh Wex,11 Reem A. Mustafa,12,13 Rebecca L. Morgan,12 and
Nancy Santesso12
1Department of Medicine and 2Department of Pathology and Laboratory Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA; 3Department of
Medicine, Duke University Medical Center, Durham, NC; 4Department of Haematology, University of New South Wales, Sydney, NSW, Australia; 5Institute of Immunology and
Transfusion Medicine, University of Greifswald, Greifswald, Germany; 6Department of Haematology-Haemostasis, Trousseau Hospital, Tours, France; 7Department of
Medicine, McMaster University, Hamilton, ON, Canada; 8New York, NY; 9Department of Anaesthesiology, University of Greifswald, Greifswald, Germany; 10Department of
Pathology and Molecular Medicine, McMaster University, Hamilton, ON, Canada; 11Columbus, OH; 12Department of Health Research Methods, Evidence and Impact,
McMaster University, Hamilton, ON, Canada; and 13Department of Medicine, University of Missouri–Kansas City, Kansas City, MO
Background: Heparin-induced thrombocytopenia (HIT) is an adverse drug reaction mediated by
platelet-activating antibodies that target complexes of platelet factor 4 and heparin. Patients are at
markedly increased risk of thromboembolism.
Objective: These evidence-based guidelines of the American Society of Hematology (ASH) are
intended to support patients, clinicians, and other health care professionals in their decisions about
diagnosis and management of HIT.
Methods: ASH formed a multidisciplinary guideline panel balanced to minimize potential bias from
conflicts of interest. The McMaster University GRADE Centre supported the guideline development
process, including updating or performing systematic evidence reviews. The panel prioritized clinical
questions and outcomes according to their importance for clinicians and patients. The Grading of
Recommendations Assessment, Development and Evaluation (GRADE) approach was used to assess
evidence and make recommendations, which were subject to public comment.
Results: The panel agreed on 33 recommendations. The recommendations address screening of
asymptomatic patients for HIT, diagnosis and initial management of patients with suspected HIT,
treatment of acute HIT, and special situations in patients with acute HIT or a history of HIT, including
cardiovascular surgery, percutaneous cardiovascular intervention, renal replacement therapy, and
venous thromboembolism prophylaxis.
Conclusions: Strong recommendations include use of the 4Ts score rather than a gestalt approach for
estimating the pretest probability of HIT and avoidance of HIT laboratory testing and empiric treatment of
HIT in patients with a low-probability 4Ts score. Conditional recommendations include the choice among
non-heparin anticoagulants (argatroban, bivalirudin, danaparoid, fondaparinux, direct oral anticoagulants)
for treatment of acute HIT.
Summary of recommendations
These guidelines are based on updated and original systematic reviews of evidence conducted under
the direction of the McMaster University Grading of Recommendations Assessment, Development and
Evaluation (GRADE) Centre with international collaborators. The panel followed best practice for
guideline development recommended by the Institute of Medicine and the Guidelines International
Network.1-4 The panel used the GRADE approach5-11 to assess the certainty in the evidence and
formulate recommendations.
Heparin-induced thrombocytopenia (HIT) is a prothrombotic adverse drug reaction, mediated in most
cases by immunoglobulin G antibodies that target complexes of platelet factor 4 (PF4) and heparin.12
Submitted 9 August 2018; accepted 14 September 2018. DOI 10.1182/
bloodadvances.2018024489.
Resources for implementing these guidelines, including apps, patient decision aids,
and teaching slide sets, may be accessed at the ASH web page hematology.org/vte.
The full-text version of this article contains a data supplement.
© 2018 by The American Society of Hematology
3360 27 NOVEMBER 2018 x VOLUME 2, NUMBER 22
Unfractionated heparin (UFH) and low-molecular-weight heparin
(LMWH) are the most widely used anticoagulants in the world among
hospitalized patients. Approximately 12 million inpatients in the United
States alone are exposed to heparin each year.13 The incidence of HIT
among these patients ranges from ,0.1% to 7%, depending on the
type of heparin (UFH vs LMWH), duration of heparin exposure, and
patient population (eg, surgical vs medical).14-16 One-third to one-half
of cases of HIT are complicated by thrombosis, which may be venous
or arterial and may be limb- or life-threatening.17-19 Recommendations
in this guideline focus on the 5 phases of HIT (defined in Table 1) and
address screening of asymptomatic patients for HIT, diagnosis and
initial management of patients with suspected HIT, treatment of acute
HIT, and special situations in patients with acute HIT or a history of
HIT, including cardiovascular surgery, percutaneous cardiovascular
intervention (PCI), renal replacement therapy, and venous thrombo-
embolism (VTE) prophylaxis.
Interpretation of strong and
conditional recommendations
The strength of a recommendation is expressed as either strong
(“the guideline panel recommends...”) or conditional (“the guideline
panel suggests…”) and has the following interpretation:
Strong recommendation
c For patients: most individuals in this situation would want the
recommended course of action, and only a small proportion
would not.
c For clinicians: most individuals should follow the recommended
course of action. Formal decision aids are not likely to be needed
to help individual patients make decisions consistent with their
values and preferences.
c For policy makers: the recommendation can be adopted as
policy in most situations. Adherence to this recommendation
according to the guideline could be used as a quality criterion or
performance indicator.
c For researchers: the recommendation is supported by credible
research or other convincing judgments that make additional
research unlikely to alter the recommendation. On occasion, a
strong recommendation is based on low or very low certainty in
the evidence. In such instances, further research may provide
important information that alters the recommendation.
Conditional recommendation
c For patients: the majority of individuals in this situation would want
the suggested course of action, but many would not. Decision aids
may be useful in helping patients to make decisions consistent with
their individual risks, values, and preferences.
c For clinicians: different choices will be appropriate for individ-
ual patients, and clinicians must help each patient arrive at a
management decision consistent with the patient’s values and
preferences. Decision aids may be useful in helping individuals
make decisions consistent with their individual risks, values, and
preferences.
c For policy makers: policy making will require substantial debate
and involvement of various stakeholders. Performance measures
about the suggested course of action should focus on whether
an appropriate decision-making process is duly documented.
c For researchers: this recommendation is likely to be strength-
ened (for future updates or adaptation) by additional research.
An evaluation of the conditions and criteria (and the related
judgments, research evidence, and additional considerations)
that determined the conditional (rather than strong) recommen-
dation will help identify possible research gaps.
Recommendations
Screening asymptomatic patients for HIT
Recommendation 1.1.a. For patients receiving heparin in
whom the risk of HIT is considered low (,0.1%), the American
Society of Hematology (ASH) guideline panel suggests against
platelet count monitoring to screen for HIT (conditional recommen-
dation, very low certainty in the evidence about effects Å◯◯◯).
Recommendation 1.1.b. For patients receiving heparin in
whom the risk of HIT is considered intermediate (0.1%-1.0%) or
high (.1.0%), the ASH guideline panel suggests platelet count
monitoring to screen for HIT. If the patient has received heparin in
the 30 days before the current course of heparin, the ASH guideline
panel suggests platelet count monitoring beginning on day 0 (the
day heparin is initiated). If the patient has not received heparin in the
30 days before the current course of heparin, the ASH guideline
panel suggests monitoring the platelet count from day 4 until day 14
or until heparin is stopped, whichever occurs first, if practicable. In
high-risk patients, the ASH guideline panel suggests monitoring the
platelet count at least every other day. In intermediate-risk patients,
the ASH guideline panel suggestsmonitoring the platelet count every
2 to 3 days (conditional recommendations, very low certainty in the
evidence about effects Å◯◯◯). Remarks: Low-risk patients include
medical and obstetrical patients receiving LMWH, patients receiving
LMWH after minor surgery or minor trauma, and any patients receiving
fondaparinux. Intermediate-risk patients include medical and obstetrical
patients receiving UFH and patients receiving LMWH after major
surgery or major trauma. High-risk populations include surgical and
trauma patients receiving postoperative UFH. Some patients may
receive a combination of UFH and LMWH or UFH and fondaparinux;
these patients should be considered to belong to the UFH group.
In patients at intermediate or high risk for HIT who have not received
heparin in the 30 days prior to the current course of heparin, some
clinicians may choose to begin monitoring the platelet count before
day 4, because platelet count values before day 4 may aid in the
interpretation of platelet count values beyond day 4.
Diagnosis and initial management of patients with
suspected HIT
Recommendations 2.1 to 2.10 should be considered together
when patients with suspected HIT are being tested and treated. The
recommendations and sequence of tests and treatment are
illustrated in Figure 1.
Recommendation 2.1. In patients with suspected HIT, the ASH
guideline panel recommends using the 4Ts score to estimate the
probability of HIT rather than a gestalt approach. If there is an
intermediate- or high-probability 4Ts score, the ASH guideline panel
recommends an immunoassay (strong recommendations, moderate
certainty in the evidence about effectsÅÅÅ◯). If the immunoassay is
positive and a functional assay is available (either locally or as a send-
out test to a reference laboratory), the ASH guideline panel suggests
27 NOVEMBER 2018 x VOLUME 2, NUMBER 22 ASH 2018 VTE GUIDELINES: HIT 3361
a functional assay (conditional recommendation, moderate certainty
in the evidence about effects ÅÅÅ◯).
Remarks: Missing or inaccurate information may lead to a faulty
4Ts score and inappropriate management decisions. Every effort
should be made to obtain accurate and complete information
necessary to calculate the 4Ts score. If key information is missing, it
may be prudent to err on the side of a higher 4Ts score. Patients
should be reassessed frequently. If there is a change in the clinical
picture, the 4Ts score should be recalculated.
Different immunoassays and functional assays are available. The
choice of assay may be influenced by diagnostic accuracy, availability,
cost, feasibility, and turnaround time. If an enzyme-linked immunoassay
(ELISA) is used, a low threshold is preferred over a high threshold. In
some settings, a functional assay may not be available, and decisions
may need to be made on the basis of the results of the 4Ts score and
immunoassay. In general, the likelihood of HIT increases with a higher
4Ts score and a higher ELISA optical density (OD). A functional assay
may not be necessary for patients with a high-probability 4Ts score
and very strongly positive immunoassay (eg, an ELISA value of .2.0
OD units). In some centers, a functional assay may be performed in
tandem with an immunoassay for quality assurance or efficiency.
Recommendation 2.2. In patients with suspected HIT and a
low-probability 4Ts score, the ASH guideline panel recommends
against HIT laboratory testing (strong recommendation, moderate
certainty in the evidence about effects ÅÅÅ◯). Remark: HIT
laboratory testing may be appropriate for patients with a low-
probability 4Ts score if there is uncertainty about the 4Ts score (eg,
because of missing data).
Recommendation 2.3. In patients with suspected HIT and a low-
probability 4Ts score, the ASH guideline panel recommends against
empiric treatment of HIT (ie, against discontinuation of heparin and
initiation of a non-heparin anticoagulant) (strong recommendation,
moderate certainty in the evidence about effects ÅÅÅ◯).
Recommendation 2.4.a. In patients with suspected HIT and an
intermediate-probability 4Ts score who have no other indication for
therapeutic-intensity anticoagulation, the ASH guideline panel
recommends discontinuation of heparin (strong recommendation,
moderate certainty in the evidence about effects ÅÅÅ◯).
Recommendation 2.4.b. The ASH guideline panel suggests
initiation of a non-heparin anticoagulant at prophylactic intensity
if the patient is at high risk of bleeding and at therapeutic
intensity if the patient is not at high risk of bleeding (conditional
recommendation, moderate certainty in the evidence about
effects ÅÅÅ◯).
Recommendation 2.5.a. In patients with suspected HIT and an
intermediate-probability 4Ts score who have another indication for
therapeutic-intensity anticoagulation, the ASH guideline panel
recommends discontinuation of heparin (strong recommendation,
moderate certainty in the evidence about effects ÅÅÅ◯).
Recommendation 2.5.b. The ASH guideline panel suggests
initiation of a non-heparin anticoagulant at therapeutic intensity
(conditional recommendation, moderate certainty in the evidence
about effects ÅÅÅ◯).
Recommendation 2.6. In patients with suspected HIT and a
high-probability 4Ts score, the ASH guideline panel recommends
discontinuation of heparin and initiation of a non-heparin anticoag-
ulant at therapeutic intensity (strong recommendation, moderate
certainty in the evidence about effects ÅÅÅ◯).
Recommendation 2.7. In patients with an intermediate-probability
4Ts score and a negative immunoassay, the ASH guideline panel
recommends discontinuation of the non-heparin anticoagulant and
resumption of heparin, if indicated (strong recommendation, moderate
certainty in the evidence about effects ÅÅÅ◯).
Recommendation 2.8. In patients with a high-probability 4Ts
score and a negative immunoassay, the ASH guideline panel
recommends discontinuation of the non-heparin anticoagulant and
resumption of heparin, if indicated (strong recommendation, moder-
ate certainty in the evidence about effectsÅÅÅ◯). Remark: Rarely,
patients with HIT may have a negative immunoassay, either because
of a laboratory error or because the pathologic antigen involves a
complex of heparin and a molecule other than PF4. Clinical
reevaluation, a repeat immunoassay, a different immunoassay, and/
or a functional assay may be helpful in clarifying the diagnosis.
Recommendation 2.9. In patients with an intermediate-
probability 4Ts score and a positive immunoassay, the ASH
guideline panel recommends continued avoidance of heparin and
continued administration of a non-heparin anticoagulant at thera-
peutic intensity. For patients who were receiving prophylactic-
intensity anticoagulation, the ASH guideline panel recommends
providing therapeutic-intensity anticoagulation (strong recommen-
dations, moderate certainty in the evidence about effects ÅÅÅ◯).
Recommendation 2.10. In patients with a high-probability 4Ts
score and a positive immunoassay, the ASH guideline panel
recommends continued avoidance of heparin and continued
Table 1. The 5 phases of HIT
Phase Platelet count Functional assay Immunoassay Recommendations
Suspected HIT Decreased ? ? 2.1-2.10
Acute HIT Decreased 1 1 3.1-3.8, 4.1, 5.1, 6.1, 8.1.a
Subacute HIT A Normal 1 1 3.9, 4.1, 5.1, 6.2, 8.1.a
Subacute HIT B Normal – 1 4.2, 5.2, 6.2, 8.1.a
Remote HIT Normal – – 4.2, 5.2, 6.2, 7.1, 8.1.b
Patients with suspected HIT are those who are thought to have HIT on clinical grounds but for whom confirmatory laboratory test results are not yet available. Once the diagnosis is
confirmed, the patient is labeled as having acute HIT, a highly prothrombotic phase which persists until platelet count recovery. Subacute HIT A is the phase following platelet count recovery
but before the functional assay becomes negative. Subacute HIT B is the interval after the functional assay becomes negative but before the immunoassay becomes negative. Finally, once
anti-PF4 or anti-heparin antibodies are no longer detectable by immunoassay, the patient is said to have remote HIT. Applicable recommendations are listed for each of the 5 phases of HIT.
Adapted from Cuker.41
3362 CUKER et al 27 NOVEMBER 2018 x VOLUME 2, NUMBER 22
administration of a non-heparin anticoagulant at therapeutic intensity
(strong recommendation, moderate certainty in the evidence about
effects ÅÅÅ◯).
Management of the acute phase of HIT
Recommendation 3.1. In patients with acute HIT complicated by
thrombosis (HITT) or acute HIT without thrombosis (isolated HIT), the
ASH guideline panel recommends discontinuation of heparin and
initiation of a non-heparin anticoagulant (strong recommendation,
moderate certainty in the evidence about effectsÅÅÅ◯).When a non-
heparin anticoagulant is being selected, the ASH guideline panel
suggests argatroban, bivalirudin, danaparoid, fondaparinux, or a direct
oral anticoagulant (DOAC) (conditional recommendation, very low
certainty in the evidence about effects Å◯◯◯).
Remarks: The choice of agent may be influenced by drug factors
(availability, cost, ability to monitor the anticoagulant effect, route of
HIT unlikely;
Do not order HIT lab testing;
Continue/resume heparin if
indicated;
Discontinue non-heparin
anticoagulant (if applicable)
HIT likely;
See “Management
of the acute phase
of HIT” for
management
recommendations
Positive
Positive Negative
Obtain immunoassayc
Negativef
Obtain functional assaye
Continue to avoid heparin;
Continue non-heparin anticoagulantd
Discontinue heparin; Start non-
heparin anticoagulantb
Low clinical probability
(4Ts score 3)a
Intermediate/high clinical
probability (4Ts score 4)a
Calculate 4Ts score
HIT Suspected
2.1
2.1
2.4, 2.5, 2.6
2.1
2.9, 2.10
2.1 2.7, 2.8
2.2, 2.3
Figure 1. Algorithm for the diagnosis and initial management of patients with suspected HIT. Numbered recommendations are listed in the corresponding portion
of the algorithm. Actions are in dark gray boxes; test results are in light gray boxes. aMissing or inaccurate information may lead to a faulty 4Ts score and inappropriate management decisions.
Every effort should be made to obtain accurate and complete information necessary to calculate the 4Ts score. If key information is missing, it may be prudent to err on the side of a higher
4Ts score. HIT laboratory testing may be appropriate for patients with a low-probability 4Ts score if there is uncertainty about the 4Ts score (eg, because of missing data). Patients should be
reassessed frequently. If there is a change in the clinical picture, the 4Ts score should be recalculated. bIf the patient has an intermediate-probability 4Ts score, has no other indication for
therapeutic-intensity anticoagulation, and is judged to be at high risk for bleeding, the panel suggests treatment with a non-heparin anticoagulant at prophylactic intensity rather than therapeutic
intensity. If the patient has an intermediate-probability 4Ts score and is not judged to be at high risk for bleeding or has another indication for therapeutic-intensity anticoagulation, the panel
suggests treatment with a non-heparin anticoagulant at therapeutic intensity rather than prophylactic intensity. In a patient with a high-probability 4Ts score, the panel recommends treatment
with a non-heparin anticoagulant at therapeutic intensity. cDifferent immunoassays are available. The choice of assay may be influenced by accuracy, availability, cost, feasibility, and turnaround
time. If an enzyme-linked immunoassay is used, a lower threshold is preferred over a high threshold. dFor all patients with a positive immunoassay, including those who were receiving
prophylactic-intensity treatment with a non-heparin anticoagulant before the availability of the immunoassay result, the panel recommends treatment with a non-heparin anticoagulant at
therapeutic intensity. eDifferent functional assays are available. The choice of assay may be influenced by accuracy, availability, cost, feasibility, and turnaround time. In some settings, a
functional assay may not be available, and decisions may need to be made on the basis of the results of the 4Ts score and immunoassay. A functional assay may not be necessary in patients
with a high 4Ts score and a strongly positive immunoassay. fMost patients with a negative functional assay do not have HIT and may be managed accordingly. However, depending on the
type of functional assay and the technical expertise of the laboratory, false-negative results are possible. Therefore, a presumptive diagnosis of HIT may be considered for some patients with a
negative functional assay, especially if there is a high-probability 4Ts score and a strongly positive immunoassay (represented in the figure by a dashed line).
27 NOVEMBER 2018 x VOLUME 2, NUMBER 22 ASH 2018 VTE GUIDELINES: HIT 3363
administration, and half-life), patient factors (kidney function, liver
function, bleeding risk, and clinical stability), and experience of the
clinician.
In patients with critical illness, increased bleeding risk, or increased
potential need for urgent procedures, argatroban or bivalirudin may
be preferred because of shorter duration of effect. These patients
may require close monitoring. In patients with moderate or severe
hepatic dysfunction (Child-Pugh class B and C), it is advisable to
avoid argatroban or use a reduced dose.
Fondaparinux and the DOACs are reasonable options in clinically
stable patients at average risk of bleeding. The same contraindica-
tions to their use in the treatment of acute VTE should be applied in
determining their appropriateness for patients with HIT.
In patients with HIT complicated by life- or limb-threatening
thromboembolism (eg, massive pulmonary embolism or venous
limb gangrene), a parenteral non-heparin anticoagulant may be
preferred because few such patients have been treated with a
DOAC.
With respect to the choice of DOAC, most of the published
experience in HIT is with rivaroxaban. Various dosing regimens have
been reported. For patients with acute HITT, rivaroxaban at a dose
of 15 mg twice per day for 3 weeks followed by 20 mg once per day
is preferred. For patients with acute isolated HIT, rivaroxaban 15 mg
twice per day until platelet count recovery (usually a platelet count
of $150 3 109/L) followed by 20 mg once per day is preferred if
there is an indication for ongoing anticoagulation.
Recommendation 3.2. In patients with acute HITT or acute
isolated HIT, the ASH guideline panel recommends treatment with a
non-heparin anticoagulant at therapeutic-intensity dosing rather
than prophylactic-intensity dosing (strong recommendation, very
low certainty in the evidence about effects Å◯◯◯).
Recommendation 3.3. In patients with acute HITT or acute
isolated HIT and no other indication for antiplatelet therapy, the
ASH guideline panel suggests treatment with a non-heparin
anticoagulant alone rather than in combination with an antiplatelet
agent (conditional recommendation, low certainty in the evidence
about effects ÅÅ◯◯). Remark: In patients with acute HITT or
acute isolated HIT and another indication for antiplatelet therapy
(eg, coronary artery disease or recent coronary stent placement),
the decision to continue antiplatelet therapy during treatment with a
non-heparin anticoagulant may be influenced by the risk of vascular
events and bleeding.
Recommendation 3.4. In patients with acute HITT or acute
isolated HIT, the ASH guideline panel recommends against routine
insertion of an inferior vena cava (IVC) filter (strong recommenda-
tion, moderate certainty in the evidence about effects ÅÅÅ◯).
Recommendation 3.5. In patients with acute HITT or acute
isolated HIT, the ASH guideline panel recommends against initiation
of a vitamin K antagonist (VKA) before platelet count recovery (usually
a platelet count of $150 3 109/L) (strong recommendation,
moderate certainty in the evidence about effects ÅÅÅ◯). Remark:
This recommendation also applies to patients who are taking a VKA
at the onset of acute HITT or acute isolated HITT. In these patients,
the VKA would be discontinued, and intravenous vitamin K would be
administered concomitant with initiation of a non-heparin anticoag-
ulant (see recommendations 3.1, 3.2, and 3.4).
Recommendation 3.6. In patients with acute HITT or acute
isolated HIT who are at average bleeding risk, the ASH guideline
panel suggests against routine platelet transfusion (conditional
recommendation, low certainty in the evidence about effects
ÅÅ◯◯). Remark: Platelet transfusion may be an option for
patients with active bleeding or at high risk of bleeding.
Recommendation 3.7.a. In patients with acute isolated HIT, the
ASH guideline panel suggests bilateral lower-extremity compres-
sion ultrasonography to screen for asymptomatic proximal deep
vein thrombosis (DVT) (conditional recommendation, very low
certainty in the evidence about effects Å◯◯◯).
Recommendation 3.7.b. In patients with acute isolated HIT and
an upper-extremity central venous catheter (CVC), the ASH
guideline panel suggests upper-extremity ultrasonography in the
limb with the catheter to screen for asymptomatic DVT. The ASH
guideline panel suggests against upper-extremity ultrasonography
in limbs without CVCs to screen for asymptomatic DVT (conditional
recommendations, very low certainty in the evidence about effects
Å◯◯◯).Remark: These recommendations do not apply to patients
with signs or symptoms suggestive of DVT for whom diagnostic
imaging would be indicated.
Recommendation 3.8. In patients with acute isolated HIT and
no asymptomatic DVT identified by screening compression
ultrasonography, the ASH guideline panel suggests that anti-
coagulation be continued, at a minimum, until platelet count
recovery (usually a platelet count of $150 3 109/L). The ASH
guideline panel suggests against continuing treatment for $3
months unless the patient has persisting HIT without platelet count
recovery (conditional recommendations, very low certainty in the
evidence Å◯◯◯). Remark: These recommendations apply only to
patients with isolated HIT. The ASH guideline panel did not address
the duration of anticoagulation in patients with acute HITT and no
other indication for anticoagulation in whom anticoagulation is
typically given for 3 to 6 months.
Recommendation 3.9. In patients with subacute HIT A, the ASH
guideline panel suggests treatment with a DOAC (eg, dabigatran,
rivaroxaban, or apixaban) rather than a VKA (conditional recommen-
dation, moderate certainty in the evidence about effects ÅÅÅ◯).
Remarks: The choice of agent may be influenced by drug factors
(availability, cost, ability to monitor the anticoagulant effect, route of
administration, and half-life), patient factors (kidney function, liver function,
bleeding risk, and clinical stability), and experience of the clinician.
DOACs are preferred for clinically stable patients at average
bleeding risk. The same contraindications to their use in the
treatment of acute VTE should be applied in determining their
appropriateness for patients with HIT.
Cardiovascular surgery
Good practice statement 4.1.a. In patients with acute HIT or
subacute HIT A who require cardiovascular surgery, the ASH
guideline panel agrees that surgery should be delayed until the
patient has subacute HIT B or remote HIT (see recommendation
4.2), if feasible.
Recommendation 4.1.b. If delaying surgery is not feasible, the
ASH guideline panel suggests one of the following: intraoperative
anticoagulation with bivalirudin, intraoperative heparin after
3364 CUKER et al 27 NOVEMBER 2018 x VOLUME 2, NUMBER 22
treatment with preoperative and/or intraoperative plasma exchange,
or intraoperative heparin in combination with a potent antiplatelet
agent (eg, prostacyclin analog or tirofiban) (conditional recommen-
dation, low certainty in the evidence about effects ÅÅ◯◯).
Remarks: The choice of strategy may be influenced by availability,
cost, and clinician experience. Consensus protocols for the plasma
exchange and intraoperative heparin strategy and for the intraoperative
heparin and potent antiplatelet agent strategy have not been established.
If either of these strategies is used, treatment with heparin is limited to the
intraoperative setting and avoided before and after surgery.
Recommendation 4.2. In patients with subacute HIT B or
remote HIT who require cardiovascular surgery, the ASH guideline
panel suggests intraoperative anticoagulation with heparin rather
than treatment with a non-heparin anticoagulant or plasma
exchange and heparin or heparin combined with an antiplatelet agent
(conditional recommendation, very low certainty in the evidence about
effectsÅ◯◯◯).Remarks: Treatment with heparin would be limited to
the intraoperative setting and avoided before and after surgery.
Postoperative platelet count monitoring for HIT may be necessary,
even when postoperative heparin is not given, because delayed-onset
(autoimmune) HIT beginning 5 to 10 days after the intraoperative
heparin exposure has been reported.
Percutaneous cardiovascular intervention
Recommendation 5.1. In patients with acute HIT or subacute
HIT A who require PCI, the ASH guideline panel suggests treatment
with bivalirudin rather than a different non-heparin anticoagulant
(conditional recommendation, low certainty in the evidence ÅÅ◯◯).
Remarks: If bivalirudin is not available or there is a lack of institutional
experience, argatroban might be a suitable substitute. The choice of
drug may be influenced by drug availability, cost, ability to monitor the
anticoagulant effect, and clinician experience.
Recommendation 5.2. In patients with subacute HIT B or
remote HIT who require PCI, the ASH guideline panel suggests
treatment with bivalirudin rather than UFH (conditional recommen-
dation, very low certainty in the evidence Å◯◯◯).
Remarks: Heparin is an acceptable alternative for patients with
subacute HIT B or remote HIT if a suitable non-heparin anticoagulant is
not available or clinician experience is lacking. If heparin is used,
exposure should be limited to the intraprocedural setting and should be
avoided before and after the procedure.
If bivalirudin is not available or there is a lack of institutional
experience, argatroban might be a suitable substitute. The choice of
drug may be influenced by drug availability, cost, ability to monitor
the anticoagulant effect, and clinician experience.
Renal replacement therapy
Recommendation 6.1. In patients with acute HIT who are
receiving renal replacement therapy and require anticoagulation to
prevent thrombosis of the dialysis circuitry, the ASH guideline panel
suggests treatment with argatroban, danaparoid, or bivalirudin rather
than other non-heparin anticoagulants (conditional recommendation;
very low certainty in the evidence about effects Å◯◯◯). Remark:
The choice of agent may be influenced by drug factors (availability,
cost), patient factors (liver function), and experience of the clinician.
Recommendation 6.2. In patients with subacute HIT A, sub-
acute HIT B, or remote HIT who are receiving renal replacement
therapy, are not otherwise receiving anticoagulation, and require
anticoagulation to prevent thrombosis of the dialysis circuit, the
ASH guideline panel suggests regional citrate rather than heparin or
other non-heparin anticoagulants (conditional recommendation; very
low certainty in the evidence about effects Å◯◯◯). Remark:Citrate
is not appropriate for patients with acute HIT, who require systemic
rather than regional anticoagulation (see recommendation 6.1).
VTE treatment and prophylaxis in patients with
remote HIT
Recommendation 7.1. In patients with remote HIT who require
VTE treatment or prophylaxis, the ASH guideline panel recom-
mends administration of a non-heparin anticoagulant (eg, apixaban,
dabigatran, danaparoid, edoxaban, fondaparinux, rivaroxaban, or
VKA) rather than UFH or LMWH (strong recommendation, very low
certainty in the evidence about effects Å◯◯◯). Remarks: For
recommendations on choice of non-heparin anticoagulant for
VTE prophylaxis, please refer to the American Society of Hematology
Guidelines on Prevention of Venous Thromboembolism in Surgical
Hospitalized Patients (manuscript in preparation) and Prophylaxis for
Hospitalized andNonhospitalizedMedical Patients (Schünemann HJ et
al,Blood Advances, in press). For recommendations on choice of agent
for VTE treatment, please refer to the American Society of Hematology
Guidelines on Treatment of Acute VTE (manuscript in preparation).
Emergency identification
Recommendation 8.1.a. In patients with a history of HIT in the
past 3 months, the ASH guideline panel suggests carrying or
wearing an emergency identifier (eg, an emergency pendant or
bracelet) (conditional recommendation, very low certainty in the
evidence about effects Å◯◯◯). Remark: The emergency identifier
should include the drug (heparin), the reaction to the drug (HIT),
and the date HIT was diagnosed.
Recommendation 8.1.b. In patients with a history of HIT more
than 3 months ago, the ASH panel suggests against carrying or
wearing an emergency identifier (conditional recommendation, very
low certainty in the evidence about effects Å◯◯◯).
Values and preferences
For most recommendations, the ASH guideline panel placed a high
value on avoiding death, limb amputation, and new thrombotic events.
The values were based on literature showing that most people find that
DVT and pulmonary embolism likely have an impact on their lives.
When considering the effects of different diagnostic strategies, the
ASH guideline panel placed a higher value on avoiding false negatives
(ie, missing true HIT cases) and a lower value on avoiding false
positives (ie, treating patients who do not have true HIT). The high value
placed on false negatives was a result of the high risk of death, limb
amputation, and thrombosis associated with a delay in initiation of
appropriate therapy in patients with true HIT.17,20 The panel perceived
these risks to exceed the harms of false-positive diagnosis, which
are nonetheless substantial and include non-heparin anticoagulant-
associated major bleeding, unnecessary suspension of heparin, and
inappropriate withholding of heparin in patients who have been
mislabeled as having a heparin allergy.
Explanations and other considerations
These recommendations take into consideration cost and cost-
effectiveness and the impact on equity, acceptability, and feasibility.
27 NOVEMBER 2018 x VOLUME 2, NUMBER 22 ASH 2018 VTE GUIDELINES: HIT 3365
Some recommendations address selection of a non-heparin antico-
agulant among multiple options. The ASH guideline panel agreed that
some agents may not be accessible in all institutions or jurisdic-
tions and may not be affordable for all patients. In addition, experi-
ence with these medications may vary among clinicians, which may
influence the choice of agent. Similar issues were considered when
recommendations were made about different laboratory tests for
diagnosing HIT. Although immunoassays are widely available and the
turnaround time for results is relatively rapid, functional assays are not
available in most institutions, and additional cost and wait time may be
incurred if the test needs to be sent to a reference laboratory for
analysis, thus limiting the feasibility of implementing some strategies.
Introduction
Aims of these guidelines and specific objectives
The purpose of these guidelines is to provide evidence-based
recommendations about the diagnosis and management of HIT.
The target audience includes patients, hematologists, internists,
surgeons, hospitalists, intensivists, anesthesiologists, other
clinicians, and decision makers. Policy makers interested in
these guidelines include those involved in developing local,
national, or international protocols with the goal of improving the
diagnosis and management of patients with HIT and evaluating
direct and indirect harms related to HIT. This article may also
serve as the basis for adaptation by local, regional, or national
guideline panels.
Description of the health problems
HIT is an iatrogenic disorder mediated in most cases by immuno-
globulin G antibodies that target multimolecular complexes of PF4
and heparin.12,21 These antibodies engender a hypercoagulable state
through activation of platelets and generation of procoagulant
platelet-derived microparticles as well as activation of monocytes,
neutrophils, and endothelial cells, with resultant elaboration of tissue
factor and proadhesive surface molecules.22-26 The end result of
these changes is a profound thrombotic tendency. Thrombosis
occurs in one-third to one-half of patients with HIT and may be
venous, arterial, or microvascular.17-19 Rates of amputation are;1%
to 3%, and rates of death associated with HIT are ;5% to
10%.17,27-31 Although HIT is associated with a decrease in platelet
count, as its name implies, clinically significant bleeding at pre-
sentation is uncommon.32
UFH and LMWH are widely used in hospitalized patients.
Approximately 12 million inpatients in the United States alone are
exposed to heparin each year.13 The incidence of HIT among these
patients ranges from ,0.1% to 7% depending on the type of
heparin, duration of heparin exposure, and patient population. UFH
is associated with an ;10-fold greater risk of HIT than LMWH,14
whereas the risk with fondaparinux is negligible.33,34 HIT occurs in
2% to 3% of patients who receive UFH for 6 or more consecutive
days but is significantly less common with more abbreviated
courses of treatment.14,15 HIT occurs with approximately threefold-
greater frequency in surgical and major trauma patients than in
medical patients and is rarely observed in pediatric and obstetrical
populations.35-38
The clinical and immunologic response to heparin in a patient with
acute HIT follows a predictable pattern after discontinuation of
heparin. Platelet count recovery occurs within 7 days in 90% of
cases, although it may take weeks in a minority of patients.39,40
Functional assays become negative at a median of 50 days after
heparin is suspended. Circulating anti-PF4/heparin antibodies are
no longer detectable by immunoassay at a median of 85 days.39
This stereotyped pattern of events allows HIT to be conceptually
divided into 5 sequential phases (Table 1).41 In suspected HIT, the
patient is thought to have HIT on clinical grounds, but confirmatory
laboratory test results are not yet available. Once the diagnosis is
confirmed, the patient is labeled as having acute HIT, a highly
prothrombotic phase that persists until platelet count recovery.
Subacute HIT A is the phase after platelet count recovery but
before the functional assay becomes negative. Subacute HIT B is
the interval after the functional assay becomes negative but
before the immunoassay becomes negative. Finally, once anti-
PF4/heparin antibodies are no longer detectable by immunoas-
say, the patient is said to have remote HIT. Each phase of HIT
confronts the clinician with a unique set of management
questions. The terms for the various phases of HIT are used in
these guidelines. Recommendations associated with each of the
5 phases are listed in Table 1.
HIT is a clinicopathologic disorder. Diagnosis rests on a careful
clinical assessment of the likelihood of HIT and HIT laboratory test
results. Left untreated, HIT is associated with an initial 5% to 10%
daily risk of thromboembolism, amputation, and death.17,20 There-
fore, in patients in whom there is sufficient suspicion, it is often
necessary to initiate empiric therapy for HIT while awaiting the
results of diagnostic laboratory testing.42 Recommendations 2.1
through 2.10 address the diagnosis and initial management of
suspected HIT and are summarized in Figure 1.
Management of acute HIT involves discontinuation of heparin and
administration of a non-heparin anticoagulant. Non-heparin antico-
agulants acceptable for the treatment of acute HIT are listed in
recommendation 3.1. Dosing and pharmacologic properties of
these agents are summarized in Table 2.
Special considerations are required for patients with a history of HIT
who require cardiovascular surgery, PCI, renal replacement therapy,
or VTE prophylaxis. These situations are addressed in recommen-
dations 4.1-4.2, 5.1-5.2, 6.1-6.2, and 7.1, respectively. Recommen-
dation 8.1 addresses the use of an emergency identifier (eg, an
emergency pendant or bracelet) for patients with a history of HIT.
Methods
The guideline panel developed and graded the recommendations
and assessed the certainty in the supporting evidence following the
GRADE approach.5-11 The overall guideline development process,
including funding of the work, panel formation, management of
conflicts of interest, internal and external review, and organizational
approval, was guided by ASH policies and procedures derived from
the Guideline International Network (GIN)-McMaster Guideline
Development Checklist (http://cebgrade.mcmaster.ca/guidecheck.
html) and was intended to meet recommendations for trustwor-
thy guidelines by the Institute of Medicine and the GIN.1-4 An
3366 CUKER et al 27 NOVEMBER 2018 x VOLUME 2, NUMBER 22
Ta
b
le
2.
N
o
n
-h
ep
ar
in
an
ti
co
ag
u
la
n
ts
fo
r
tr
ea
tm
en
t
o
f
ac
u
te
H
IT
D
ru
g
M
ec
h
an
is
m
o
f
ac
ti
o
n
R
o
u
te
o
f
ad
m
in
is
tr
at
io
n
P
ri
m
ar
y
m
ec
h
an
is
m
o
f
el
im
in
at
io
n
(h
al
f-
lif
e)
D
o
si
n
g
La
b
o
ra
to
ry
m
o
n
it
o
ri
n
g
A
rg
at
ro
ba
n
D
ire
ct
th
ro
m
bi
n
in
hi
bi
to
r
IV
H
ep
at
ob
ilia
ry
(4
0-
50
m
in
)
B
ol
us
:n
on
e
A
dj
us
tt
o
A
P
TT
1.
5-
3.
0
tim
es
ba
se
lin
e
C
on
tin
uo
u s
in
fu
si
on
:
N
or
m
al
or
ga
n
fu
nc
tio
n
→
2
m
g/
kg
/m
in
Li
ve
r
dy
sf
un
ct
io
n
(b
ilir
ub
in
.
1.
5
m
g/
dL
)
→
0.
5-
1.
2
m
g/
kg
/m
in
H
ea
rt
fa
ilu
re
,a
na
sa
rc
a,
po
st
ca
rd
ia
c
su
rg
er
y
→
0.
5-
1.
2
m
g/
kg
/m
in
B
iv
al
iru
di
n*
D
ire
ct
th
ro
m
bi
n
in
hi
bi
to
r
IV
En
zy
m
at
ic
(2
5
m
in
)
B
ol
us
:n
on
e
A
dj
us
tt
o
A
P
TT
1.
5-
2.
5
tim
es
ba
se
lin
e
C
on
tin
uo
us
in
fu
si
on
:
N
or
m
al
or
ga
n
fu
nc
tio
n
→
0.
15
m
g/
kg
/h
R
en
al
or
liv
er
dy
sf
un
ct
io
n
→
do
se
re
du
ct
io
n
m
ay
be
ap
pr
op
ria
te
D
an
ap
ar
oi
d
In
di
re
ct
fa
ct
or
X
a
in
hi
bi
to
r
IV
R
en
al
(2
4
h)
B
ol
us
:
A
dj
us
tt
o
da
na
pa
ro
id
-s
pe
ci
fic
an
ti-
X
a
ac
tiv
ity
of
0.
5-
0.
8
un
its
/m
L
,
60
kg
,1
50
0
un
its
60
-7
5
kg
,2
25
0
un
its
75
-9
0
kg
,3
00
0
un
its
.
90
kg
,3
75
0
un
its
A
cc
el
er
at
ed
in
iti
al
in
fu
si
on
:
40
0
un
its
/h
3
4
h,
th
en
30
0
un
its
/h
3
4
h
M
ai
nt
en
an
ce
in
fu
si
on
:
N
or
m
al
re
na
lf
un
ct
io
n
→
20
0
un
its
/h
R
en
al
dy
sf
un
ct
io
n
→
15
0
un
its
/h
Fo
nd
ap
ar
in
ux
*
In
di
re
ct
fa
ct
or
X
a
in
hi
bi
to
r
S
C
R
en
al
(1
7-
24
h)
,
50
kg
→
5
m
g
on
ce
pe
r
da
y
N
on
e
50
-1
00
kg
→
7.
5
m
g
on
ce
pe
r
da
y
.
10
0
kg
→
10
m
g
on
ce
pe
r
da
y
A
pi
xa
ba
n*
†
D
ire
ct
fa
ct
or
X
a
in
hi
bi
to
r
P
O
H
ep
at
ic
(8
-1
5
h)
H
IT
T:
N
on
e
10
m
g
tw
ic
e
pe
r
da
y
3
1
w
ee
k,
th
en
5
m
g
tw
ic
e
pe
r
da
y
Is
ol
at
ed
H
IT
:
5
m
g
tw
ic
e
pe
r
da
y
un
til
pl
at
el
et
co
un
t
re
co
ve
ry
D
ab
ig
at
ra
n*
†
D
ire
ct
th
ro
m
bi
n
in
hi
bi
to
r
P
O
R
en
al
(1
2-
17
h)
H
IT
T:
N
on
e
15
0
m
g
tw
ic
e
pe
rd
ay
af
te
r$
5
da
ys
of
tr
ea
tm
en
tw
ith
a
pa
re
nt
er
al
no
n-
he
pa
rin
an
tic
oa
gu
la
nt
Is
ol
at
ed
H
IT
:
15
0
m
g
tw
ic
e
pe
r
da
y
un
til
pl
at
el
et
co
un
tr
ec
ov
er
y
R
iv
ar
ox
ab
an
*†
D
ire
ct
fa
ct
or
X
a
in
hi
bi
to
r
P
O
R
en
al
(5
-9
h)
H
IT
T:
N
on
e
15
m
g
tw
ic
e
pe
r
da
y
3
3
w
ee
ks
,t
he
n
20
m
g
on
ce
pe
r
da
y
Is
ol
at
ed
H
IT
:
15
m
g
tw
ic
e
pe
r
da
y
un
til
pl
at
el
et
co
un
t
re
co
ve
ry
G
ui
da
nc
e
on
se
le
ct
in
g
an
an
tic
oa
gu
la
nt
fo
r
an
in
di
vi
du
al
pa
tie
nt
is
pr
ov
id
ed
in
th
e
re
m
ar
ks
as
so
ci
at
ed
w
ith
re
co
m
m
en
da
tio
n
3.
1.
A
P
TT
, a
ct
iv
at
ed
pa
rt
ia
lt
hr
om
bo
pl
as
tin
tim
e;
IV
,i
nt
ra
ve
no
us
;P
O
,p
er
os
;S
C
,s
ub
cu
ta
ne
ou
s.
*N
ot
ap
pr
ov
ed
fo
r
tr
ea
tm
en
to
fa
cu
te
H
IT
.
†
D
os
in
g
fo
r
tr
ea
tm
en
to
fa
cu
te
H
IT
is
no
tw
el
le
st
ab
lis
he
d.
S
ug
ge
st
ed
do
si
ng
is
ex
tr
ap
ol
at
ed
fro
m
ve
no
us
th
ro
m
bo
em
bo
lis
m
an
d
ba
se
d
on
lim
ite
d
pu
bl
is
he
d
ex
pe
rie
nc
e
in
H
IT
.
27 NOVEMBER 2018 x VOLUME 2, NUMBER 22 ASH 2018 VTE GUIDELINES: HIT 3367
article detailing the methods used to develop these guidelines is
forthcoming.
Organization, panel composition, planning,
and coordination
The work of this panel was coordinated with 9 other guideline
panels (addressing other aspects of VTE) by ASH and the
McMaster GRADE Centre (funded by ASH under a paid
agreement). Project oversight was initially provided by a co-
ordination panel, which reported to the ASH Committee on Quality,
then by the coordination panel chair (A.C.) and vice chair (Holger
Schünemann). ASH vetted and appointed individuals to the guideline
panel. The McMaster GRADE Centre vetted and retained researchers
to conduct systematic reviews of evidence and coordinate the guideline
development process, including the use of the GRADE approach. The
membership of the panel and the GRADE Centre team is described in
supplement 1.
The panel included hematologists with clinical and research
expertise on HIT, physicians from other disciplines with similar
expertise, methodologists with expertise in evidence appraisal and
guideline development, and 2 patient representatives. The panel
chair was a content expert. The vice chair was a methodologist.
In addition to synthesizing evidence systematically, the
McMaster GRADE Centre supported the guideline develop-
ment process by determining methods, preparing agendas
and meeting materials, and facilitating panel discussions. The
Panel performed its work by using Web-based tools (www.
surveymonkey.com and www.gradepro.org) and face-to-face and
online meetings.
Guideline funding and management of conflicts
of interest
Development of these guidelines was wholly funded by ASH, a
nonprofit medical specialty society that represents hematologists.
Most members of the guideline panel were members of ASH. ASH
staff supported panel appointments and coordinated meetings but
had no role in choosing the guideline questions or determining the
recommendations.
Members of the guideline panel received travel reimbursement for
attendance at in-person meetings, and the 2 patient representa-
tives each received an honorarium of $200. The panelists
received no other payments. Through the McMaster GRADE
Centre, some researchers who contributed to the systematic
evidence reviews received salary or grant support. Other
researchers participated to fulfill requirements of an academic
degree or program.
Conflicts of interest of all participants were managed according to
ASH policies on the basis of recommendations of the Institute of
Medicine43 and the GIN.4 At the time of appointment, a majority of
the guideline panel, including the chair and the vice chair, had no
conflicts of interest as defined and judged by ASH (ie, no current
material interest in any commercial entity with a product that could
be affected by the guidelines). Some panelists disclosed new
interests or relationships during the development process, but the
balance of the majority was maintained.
Before appointment to the panel, individuals disclosed both
financial and nonfinancial interests. Members of the VTE
Guideline Coordination Panel reviewed the disclosures and
judged which interests were conflicts and should be managed.
Supplement 2 provides the complete “Disclosure of Interests”
forms for all panel members. In Part A of the forms, individuals
disclosed material interests for 2 years before appointment. In
Part B, they disclosed interests that were not mainly financial. Part
C summarizes ASH decisions about which interests were judged
to be conflicts. Part D describes new interests disclosed by
individuals after appointment.
Recusal was also used to manage conflicts of interest. During
all deliberations, panel members with a current, direct financial
interest in a commercial entity with any product that could be
affected by the guidelines were recused from making judg-
ments about relevant recommendations.4,44-46 The Evidence-
to-Decision framework for each recommendation describes
which individuals were recused from making judgments about
each recommendation.
None of the McMaster-affiliated researchers who contributed to
the systematic evidence reviews or who supported the guideline
development process had any current material interest in a
commercial entity with any product that could be affected by
the guidelines. Supplement 3 provides the complete Disclosure
of Interest forms for researchers who contributed to these
guidelines.
Formulating specific clinical questions and
determining outcomes of interest
The panel used the GRADEpro Guideline Development Tool (www.
gradepro.org)47 and SurveyMonkey (www.surveymonkey.com) to
brainstorm and then prioritize the questions.
The ASH guideline panel selected outcomes of interest for each
question a priori, following an approach described in detail
elsewhere.48 In brief, the panel first brainstormed all possible
outcomes before rating their relative importance for decision-
making following the GRADE approach.48 During this rating
process, the panel used definitions of the outcomes (“marker
states”) that were developed for these guidelines. Rating outcomes
by their relative importance can help focus attention on those
outcomes that are considered most important for both clinicians
and patients and help to resolve or clarify potential disagreements.
The outcomes rated highly by the panel and those identified as
important based on the literature reviews were further refined. The
panel rated the following outcomes as critical for clinical decision
making across questions: thromboembolism, limb amputation,
mortality, major bleeding, diagnostic accuracy, pulmonary embo-
lism, IVC filter failure, hospitalization, and recurrent acute HIT.
Evidence review and development
of recommendations
For each guideline question, the McMaster GRADE Centre
prepared a GRADE Evidence-to-Decision (EtD) framework, using
the GRADEpro Guideline Development Tool (www.gradepro.
org).5,6,11 The EtD table summarized the results of systematic
reviews of the literature that were updated or performed for this
guideline. The EtD table addressed the effects of interventions,
resource use (cost-effectiveness), values and preferences
(relative importance of outcomes), equity, acceptability, and
feasibility. The guideline panel reviewed draft EtD tables
3368 CUKER et al 27 NOVEMBER 2018 x VOLUME 2, NUMBER 22
before, during, or after the guideline panel meeting and made
suggestions for corrections and identified missing evidence.
To ensure that recent studies were not missed, searches
(presented in supplement 4) were updated during December
2017, and panel members were asked to suggest any studies
that may have been considered missed and fulfilled the
inclusion criteria for the individual questions.
Under the direction of the McMaster GRADE Centre, researchers
followed the general methods outlined in the Cochrane Hand-
book for Systematic Reviews of Interventions (https://training.
cochrane.org/handbook) for conducting updated or new system-
atic reviews of intervention effects. When existing reviews were
used, judgments of the original authors about risk of bias were
either randomly checked for accuracy and accepted or con-
ducted de novo if they were not available or not reproducible.
For new reviews, risk of bias was assessed at the health
outcome level using the Cochrane Collaboration’s risk of bias
tool for randomized trials or nonrandomized studies. In addition
to conducting systematic reviews of intervention effects, the
researchers searched for evidence related to baseline risks,
values, preferences, and costs and summarized findings within
the EtD frameworks.5,6,11 Subsequently, the certainty in the body
of evidence (also known as quality of the evidence or confidence
in the estimated effects) was assessed for each effect estimate
of the outcomes of interest following the GRADE approach.
The GRADE approach was based on the following domains:
risk of bias, precision, consistency, magnitude of the estimates of
effects, directness of the evidence, risk of publication bias,
presence of large effects, and dose-response relationship, and
an assessment of the effect of residual, opposing confounding.
The certainty was categorized into 4 levels ranging from very low
to high.7-9
During a 2-day in-person meeting followed by online communi-
cation and conference calls, the panel developed clinical
recommendations based on the evidence summarized in the
EtD tables. For each recommendation, the panel took a
population perspective and came to consensus on the following:
the certainty in the evidence, the balance of benefits and harms
of the compared management options, and the assumptions
about the values and preferences associated with the decision.
The guideline panel also explicitly took into account the extent of
resource use associated with alternative management options.
The panel agreed on the recommendations (including direction
and strength), remarks, and qualifications by consensus or, in rare
instances, by voting (an 80% majority was required for a strong
recommendation) based on the balance of all desirable and
undesirable consequences. The final guidelines, including rec-
ommendations, were reviewed and approved by all members of
the panel.
Interpretation of strong and conditional recommendations
The recommendations are labeled as either “strong” or “condi-
tional,” according to the GRADE approach. The words “the
guideline panel recommends” are used for strong recommenda-
tions and “the guideline panel suggests” for conditional recom-
mendations. Table 3 provides GRADE’s interpretation of strong and
conditional recommendations by patients, clinicians, health care
policy makers, and researchers.
Document review
Draft recommendations were reviewed by all members of the panel,
revised, and then made available online on September 1, 2017, for
external review by stakeholders including allied organizations, other
medical professionals, patients, and the public. Nine individuals or
organizations submitted comments. The document was revised to
address pertinent comments, but no changes were made to
recommendations. On July 30, 2018, the ASH Guideline Oversight
Subcommittee and the ASH Committee on Quality verified that the
defined guideline development process was followed, and on August
3, 2018, the officers of the ASH Executive Committee approved
submission of the guidelines for publication under the imprimatur of
ASH. The guidelines were then subjected to peer review by Blood
Advances.
How to use these guidelines
ASH guidelines are primarily intended to help clinicians make
decisions about diagnostic and treatment alternatives. Other
purposes are to inform policy, education, and advocacy, and to
state future research needs. They may also be used by patients.
These guidelines are not intended to serve as or be construed as
a standard of care. Clinicians must make decisions on the basis
of the clinical presentation of each individual patient, ideally
through a shared process that considers the patient’s values and
preferences with respect to the anticipated outcomes of the
chosen option. Decisions may be constrained by the realities of a
specific clinical setting and local resources, including but not
limited to institutional policies, time limitations, and availability of
treatments. These guidelines may not include all appropriate
methods of care for the clinical scenarios described. As science
advances and new evidence becomes available, recommenda-
tions may become outdated. Following these guidelines cannot
guarantee successful outcomes. ASH does not warrant or
guarantee any products described in these guidelines.
Statements about the underlying values and preferences as well as
qualifying remarks accompanying each recommendation are its
integral parts and serve to facilitate more accurate interpretation.
They should never be omitted when recommendations from these
guidelines are quoted or translated. Implementation of the guidelines
will be facilitated by related interactive forthcoming decision aids.
The use of these guidelines is also facilitated by the links to the EtD
frameworks and interactive summary of findings tables in each
section.
Recommendations
Screening asymptomatic patients for HIT
Question: Should platelet count monitoring be used to screen for
HIT in patients at risk of HIT?
Recommendation 1.1.a
For patients receiving heparin in whom the risk of HIT is con-
sidered low (,0.1%), the ASH guideline panel suggests
against platelet count monitoring to screen for HIT (conditional
recommendation, very low certainty in the evidence about
effects Å◯◯◯).
27 NOVEMBER 2018 x VOLUME 2, NUMBER 22 ASH 2018 VTE GUIDELINES: HIT 3369
Recommendation 1.1.b
For patients receiving heparin in whom the risk of HIT is con-
sidered intermediate (0.1% to 1.0%) or high (.1.0%), the ASH
guideline panel suggests platelet count monitoring to screen
for HIT. If the patient has received heparin in the 30 days before
the current course of heparin, the ASH guideline panel sug-
gests platelet count monitoring beginning on day 0 (the day
heparin is initiated). If the patient has not received heparin in the
30 days before the current course of heparin, the ASH
guideline panel suggests monitoring the platelet count from
day 4 until day 14 or until heparin is stopped, whichever occurs
first, if practicable. In high-risk patients, the ASH guideline
panel suggests monitoring the platelet count at least every
other day. In intermediate-risk patients, the ASH guideline
panel suggests monitoring the platelet count every 2 to 3 days
(conditional recommendations, very low certainty in the evi-
dence about effects Å◯◯◯). Remarks: Low-risk patients in-
clude medical and obstetric patients receiving LMWH, patients
receiving LMWH after minor surgery or minor trauma, and any
patients receiving fondaparinux. Intermediate-risk populations
include medical and obstetric patients receiving UFH and pa-
tients receiving LMWH after major surgery or major trauma.
High-risk populations include surgical and trauma patients re-
ceiving postoperative UFH. Some patients may receive a
combination of UFH and LMWH or UFH and fondaparinux;
these patients should be considered to belong to the UFH
group.
In patients at intermediate or high risk for HIT who have not
received heparin in the 30 days before the current course of
heparin, some clinicians may choose to begin monitoring the
platelet count before day 4 because platelet count values be-
fore day 4 may aid in the interpretation of platelet count values
beyond day 4.
Summary of the evidence. We did not identify any
randomized or nonrandomized studies assessing platelet count
monitoring to identify HIT. Instead, evidence for the importance of
early recognition of HIT was used. To determine which patients are
at high risk of developing HIT, a meta-analysis of 15 studies primarily
in patients after orthopedic surgery and individual studies reporting
the incidence of HIT by population and type of heparin were
used.14,17,20,49 Evidence for timing and frequency of platelet count
monitoring was derived from individual studies that reported time
intervals to diagnosis and platelet recovery.39,49 The EtD framework
is shown online at https://dbep.gradepro.org/profile/DA501AC2-
CBF0-D41A-A83A-E45D3AD030D2.
Benefits. The benefit of screening would likely be greatest for
patients with a high baseline risk of HIT. A meta-analysis reported
that the incidence of HIT in postoperative (orthopedic and cardiac)
populations receiving UFH was 2.6%, but the incidence was 0.2%
in patients receiving LMWH.14 A 14-year retrospective study of 127
patients showed that surgical patients were more likely to develop
HIT than medical patients while receiving heparin thromboprophy-
laxis.17 Studies demonstrated that the typical timing of the
development of HIT after heparin initiation was 5 to 14 days.17,49
Patients who had previous recent heparin exposure, generally within
the last 30 days, were at risk of rapid-onset HIT with a fall in platelet
count occurring within hours of heparin reexposure.39,49 The
certainty in the effects of screening is very low.
Harms and burden. Evidence for harms when treatment was
delayed was found from studies reporting complications after HIT
diagnosis. A retrospective study reported that 50% of patients who
were treated with cessation of heparin alone or cessation of heparin
and initiation of warfarin experienced a thrombotic event within 30
days after diagnosis of HIT.17 A meta-analysis of trials to assess the
value of parenteral treatment with lepirudin reported a combined
event rate of death, new thromboembolic complications, and limb
amputation per patient per day of 6.1% in the period between
diagnosis of HIT and the start of therapy.20 The evidence for harms
related to monitoring is of very low certainty. No studies were found
assessing the magnitude of overdiagnosis of HIT and subsequent
treatment, although observations from the panel indicated that it
may be common and the harms may be moderately large.
Other EtD criteria and considerations. Platelet count
measurement is widely available. Although the cost of platelet count
monitoring per patient is small, monitoring all patients receiving
heparin would result in moderate costs given the frequency of
heparin use. Platelet monitoring is probably acceptable to patients
and physicians. For patients in the hospital, platelet count monitoring
is likely to be ordered for moderate- and high-risk patients for
reasons other than HIT screening. However, outpatients would
need to return to the clinic for monitoring, which is less practical.
Conclusionsand researchneeds for these recommendations.
The guideline panel determined that there is very low certainty
in the effects of platelet count monitoring in patients at risk of
HIT. The moderate benefits from early detection of HIT among
high- and moderate-risk patients would probably outweigh the
harms from overdiagnosis and inappropriate treatment. The
costs, acceptability, and feasibility also favored monitoring of
Table 3. Interpretation of strong and conditional recommendations
Implications for: Strong recommendation Conditional recommendation
Patients Most individuals in this situation would want the recommended
course of action, and only a small proportion would not.
The majority of individuals in this situation would want the
suggested course of action, but many would not.
Clinicians Most individuals should receive the intervention. Formal decision
aids are not likely to be needed to help individual patients make
decisions consistent with their values and preferences.
Different choices will be appropriate for individual patients; the
clinician must help each patient arrive at a management decision
consistent with his or her values and preferences. Decision aids
may be useful in helping individuals to make decisions consistent
with their values and preferences.
Policy makers The recommendation can be adopted as policy in most situations.
Adherence to this recommendation according to the guideline
could be used as a quality criterion or performance indicator.
Policy-making will require substantial debate and involvement of
various stakeholders.
3370 CUKER et al 27 NOVEMBER 2018 x VOLUME 2, NUMBER 22
high- and moderate-risk patients. The harms of overdiagnosis
and inappropriate treatment among low-risk patients probably
outweigh the benefits of early detection.
Diagnosis and initial management of patients with
suspected HIT
Recommendations 2.1 to 2.10 should be considered together when
testing and treating patients with suspected HIT. The recommenda-
tions and sequence of tests and treatment are illustrated in Figure 1.
Question: In patients with suspected HIT, what is the optimal
strategy for diagnosing HIT?
Recommendation 2.1
In patients with suspected HIT, the ASH guideline panel recom-
mends using the 4Ts score to estimate the probability of HIT
rather than a gestalt approach. If there is an intermediate- or high-
probability 4Ts score, the ASH guideline panel recommends an
immunoassay (strong recommendations, moderate certainty in the
evidence about effects ÅÅÅ◯). If the immunoassay is positive
and a functional assay is available (either locally or as a send-out
test to a reference laboratory), the ASH guideline panel suggests
a functional assay (conditional recommendations, moderate cer-
tainty in the evidence about effects ÅÅÅ◯).
Remarks: Missing or inaccurate information may lead to a
faulty 4Ts score and inappropriate management decisions.
Every effort should be made to obtain accurate and complete
information necessary to calculate the 4Ts score. If key in-
formation is missing, it may be prudent to err on the side of a
higher 4Ts score. Patients should be reassessed frequently. If
there is a change in the clinical picture, the 4Ts score should be
recalculated.
Different immunoassays and functional assays are available.
The choice of assay may be influenced by diagnostic accuracy,
availability, cost, feasibility, and turnaround time. If an ELISA is
used, a low threshold is preferred over a high threshold. In
some settings, a functional assay may not be available, and
decisions may need to be made on the basis of the results of
the 4Ts score and immunoassay. In general, the likelihood of
HIT increases with a higher 4Ts score and a higher ELISA
OD. A functional assay may not be necessary for patients
with a high-probability 4Ts score and very strongly positive
immunoassay (eg, an ELISA value of.2.0 OD units). In some
centers, a functional assay may be performed in tandem with
an immunoassay for quality assurance or efficiency.
Recommendation 2.2
In patients with suspected HIT and a low-probability 4Ts score,
the ASH guideline panel recommends against HIT laboratory
testing (strong recommendation, moderate certainty in the
evidence about effects ÅÅÅ◯). Remark: HIT laboratory
testing may be appropriate for patients with a low-probability
4Ts score if there is uncertainty about the 4Ts score (eg, be-
cause of missing data).
Summary of the evidence. We found 3 systematic reviews
that assessed the accuracy of the 4Ts score and the accuracy of
various immunoassays.42,50,51 The sensitivity and specificity of each
of the tests were used to model the number of true positives and
true negatives and false positives and false negatives that would
result from the use of different strategies: gestalt (unstructured,
nonstandardized, intuition-based approach to assessing pretest
probability) or 4Ts score followed by immunoassay followed by
functional assay (in the setting of a negative or positive
immunoassay), gestalt or 4Ts score followed by functional assay,
or gestalt or 4Ts score followed by immunoassay. In the model, we
assumed that the prevalence of HIT among patients with
suspected HIT is 11%42 and that the functional assay has
100% sensitivity and specificity. We used a PF4/heparin ELISA as
the immunoassay in our model and assumed a delay of 1 to several
days between when the test is ordered and when results are
available (in contrast to rapid immunoassays, for which results may
be available within minutes). We also assumed a delay of several
days in obtaining functional assay results. The effects of treatment
after a positive test using the optimal strategy were based on the
evidence for treatments in recommendations 3.1 to 3.9. The EtD
framework is shown online at https://dbep.gradepro.org/profile/
883a6eac-0bee-42b7-a788-f5998a4191d7.
Benefits, harms, and burden. On the basis of the modeled
effects of what happens to 1000 patients with suspected HIT who
have an intermediate or high 4Ts score and who have receive the
recommended strategy (Table 4, strategy 5), approximately 100
people are correctly identified as having HIT (true positives), 890
people are correctly identified as not having HIT (true negatives),
and no one is incorrectly identified as having HIT (false positives),
but 10 patients with HIT are missed (false negatives). The 10
missed patients may experience serious consequences of HIT if
they are not treated (eg, thrombosis [30% risk], amputation [6%
risk], or death [6% risk]). In total, 408 people who do not have HIT
would receive non-heparin anticoagulants unnecessarily for varying
periods of time depending on the timing of the follow-up tests.
If the 4Ts score is not used, and instead a decision to test with
immunoassay is made using a gestalt method (Table 4, strategy 2),
5 fewer people with HIT are missed, but 478 more people receive
non-heparin anticoagulants unnecessarily for varying periods of
time depending on the delay in obtaining laboratory test results.
In patients with a high 4Ts score and a strongly positive
immunoassay test (eg, an ELISA value of $2.0 OD units), no one
is incorrectly identified as having HIT (ie, no false positives), and
therefore, a follow-up functional assay is likely not necessary.
Other EtD criteria and considerations. The guideline
panel placed more value on avoiding false negatives than on
avoiding false positives because of the serious consequences of
delays in initiation of appropriate treatment, which result in higher
risks of thrombosis, amputation, and death. The panel equated 1
false negative to 10 false positives. When the relative costs of the
tests and the benefits and harms are compared, the recommended
optimal strategy of tests (Table 4, strategy 5; Figure 1) is probably
more cost-effective than not conducting a functional assay or than
testing only patients with high 4Ts scores and is more cost-effective
than using a gestalt method rather than the 4Ts score. However,
information to complete the 4Ts score may not always be available,
and although the functional assay is available either on site or as a
27 NOVEMBER 2018 x VOLUME 2, NUMBER 22 ASH 2018 VTE GUIDELINES: HIT 3371
Ta
b
le
4.
Te
st
ac
cu
ra
cy
p
er
10
00
p
at
ie
n
ts
af
te
r
ea
ch
st
ra
te
g
y
fo
r
d
ia
g
n
o
se
(1
1%
p
re
va
le
n
ce
o
f
H
IT
)
G
es
ta
lt
4T
s
Im
m
u
n
o
as
sa
y
(b
as
ed
o
n
Ig
G
E
LI
S
A
lo
w
th
re
sh
o
ld
)
95
%
C
I
F
u
n
ct
io
n
al
as
sa
y
S
en
si
tiv
ity
0.
96
9
0.
92
1
0.
98
0.
95
-0
.9
9
1.
0
S
pe
ci
fic
ity
0.
00
4
0.
54
2
0.
85
0.
78
-0
.9
1
1.
0
S
tr
at
eg
y
1.
G
es
ta
lt
2.
G
es
ta
lt
,t
h
en
IA
p
o
si
ti
ve
,t
h
en
F
A
3.
4T
s
sc
o
re
(h
ig
h
o
r
in
te
rm
ed
ia
te
)
4.
4T
s
sc
o
re
(h
ig
h
o
r
in
te
rm
ed
ia
te
),
th
en
IA
5.
4T
s
sc
o
re
(h
ig
h
o
r
in
te
rm
ed
ia
te
),
th
en
IA
p
o
si
ti
ve
,t
h
en
F
A
(r
ec
o
m
m
en
d
ed
st
ra
te
g
y)
Tr
ue
po
si
tiv
e.
P
at
ie
nt
s
w
ill
be
ap
pr
op
ria
te
ly
tr
ea
te
d
an
d/
or
ha
ve
m
or
e
te
st
in
g
(r
ed
uc
ed
ris
k
of
th
ro
m
bo
si
s
by
55
%
-7
0%
).
10
7
10
5
10
1*
99
(h
ig
h,
48
;i
nt
er
m
ed
ia
te
,5
1)
10
0
Fa
ls
e
ne
ga
tiv
e.
P
at
ie
nt
s
w
ill
be
m
is
se
d
an
d
m
ay
ex
pe
rie
nc
e
se
rio
us
co
ns
eq
ue
nc
es
of
H
IT
(e
g,
th
ro
m
bo
si
s
[3
00
of
10
00
m
or
e
pe
op
le
w
ith
H
IT
if
no
t
tr
ea
te
d]
,a
m
pu
ta
tio
n
[6
0
of
10
00
m
or
e
pe
op
le
w
ith
H
IT
if
no
tt
re
at
ed
],
de
at
h
[6
0
of
10
00
m
or
e
pe
op
le
w
ith
H
IT
if
no
t
tr
ea
te
d]
).
3
5
9
11
(h
ig
h,
1;
in
te
rm
ed
ia
te
,1
)
10
Tr
ue
ne
ga
tiv
e.
P
at
ie
nt
s
w
ill
ap
pr
op
ria
te
ly
no
th
av
e
m
or
e
te
st
in
g
an
d
w
ill
ap
pr
op
ria
te
ly
no
tb
e
tr
ea
te
d
fo
r
H
IT
.
4
89
0
48
2
82
9
(h
ig
h,
34
;i
nt
er
m
ed
ia
te
,3
13
)
89
0
Fa
ls
e
po
si
tiv
e.
P
at
ie
nt
s
w
ill
co
nt
in
ue
w
ith
un
ne
ce
ss
ar
y
te
st
in
g
an
d/
or
m
ay
ex
pe
rie
nc
e
se
rio
us
co
ns
eq
ue
nc
es
of
un
ne
ce
ss
ar
y
tr
ea
tm
en
to
fH
IT
(e
g,
bl
ee
di
ng
;
8%
to
35
%
ov
er
tr
ea
tm
en
t
du
ra
tio
n)
an
d
m
ay
be
fa
ls
el
y
la
be
le
d
as
ha
vi
ng
H
IT
ov
er
th
e
lo
ng
te
rm
.
88
6†
0
40
8*
†
61
(h
ig
h,
6;
in
te
rm
ed
ia
te
,5
5)
0
N
o.
of
im
m
un
oa
ss
ay
te
st
s
pe
rfo
rm
ed
50
9
N
o.
of
fu
nc
tio
na
la
ss
ay
te
st
s
pe
rfo
rm
ed
16
0
IA
,i
m
m
un
oa
ss
ay
;I
gG
,i
m
m
un
og
lo
bu
lin
G
;F
A
,f
un
ct
io
na
la
ss
ay
.
*E
ig
ht
y-
ni
ne
of
th
es
e
pa
tie
nt
s
w
ou
ld
ha
ve
a
hi
gh
4T
s
sc
or
e,
an
d
42
0
w
ou
ld
ha
ve
an
in
te
rm
ed
ia
te
4T
s
sc
or
e.
†
W
he
n
ge
st
al
to
r
4T
s
sc
or
e
is
fo
llo
w
ed
by
IA
an
d
FA
(w
he
n
IA
is
po
si
tiv
e)
,t
he
se
pa
tie
nt
s
w
ou
ld
re
ce
iv
e
no
n-
he
pa
rin
an
tic
oa
gu
la
nt
s
un
ne
ce
ss
ar
ily
fo
r
va
ry
in
g
pe
rio
ds
of
tim
e
de
pe
nd
in
g
on
tim
in
g
of
th
e
fo
llo
w
-u
p
te
st
s.
3372 CUKER et al 27 NOVEMBER 2018 x VOLUME 2, NUMBER 22
send-out to a reference laboratory in most settings, some institu-
tions may not have access, and equity across populations may
be reduced.
Conclusions and research needs for these recommendations.
This recommendation was based on moderate certainty in the
evidence for the diagnostic test accuracy of the tests and
management. Based on modeled effects, the recommended
strategy (Table 4, strategy 5; Figure 1) likely results in few false
negatives and few or no false positives. The tests that make up
the recommended strategy are in current use, and therefore the
strategy is feasible in most settings. Using the functional assay,
however, may not be necessary for patients with a high-
probability 4Ts score and a strongly positive immunoassay (eg,
an ELISA value of $2.0 OD units). Research priorities include
implementation analyses and identification of barriers to the use
of the recommended strategy and in particular the use of the 4Ts
score. Our modeling and recommendations apply to the PF4/
heparin ELISA. Assessment of other currently available immuno-
assays should be conducted. Research should also include the
development of novel assays that overcome the limitations of
currently available assays, such as immunoassays with enhanced
specificity and functional assays with enhanced feasibility.
Question: Should heparin be discontinued and non-heparin
anticoagulants be initiated in patients identified as being at risk of
HIT according to the 4Ts score?
Question: Should non-heparin anticoagulants be provided at
therapeutic or prophylactic intensity?
Recommendation 2.3
In patients with suspected HIT and a low-probability 4Ts score,
the ASH guideline panel recommends against empiric treat-
ment of HIT (ie, against discontinuation of heparin and initiation
of a non-heparin anticoagulant) (strong recommendation,
moderate certainty in the evidence about effects ÅÅÅ◯).
Recommendation 2.4.a
In patients with suspected HIT and an intermediate-probability
4Ts score who have no other indication for therapeutic-
intensity anticoagulation, the ASH guideline panel recom-
mends discontinuation of heparin (strong recommendation,
moderate certainty in the evidence about effects ÅÅÅ◯).
Recommendation 2.4.b
The ASH guideline panel suggests initiation of a non-
heparin anticoagulant at prophylactic intensity if the patient
is at high risk of bleeding and at therapeutic intensity if the
patient is not at high risk of bleeding (conditional recom-
mendation, moderate certainty in the evidence about ef-
fects ÅÅÅ◯).
Recommendation 2.5.a
In patients with suspected HIT and an intermediate-probability
4Ts score who have another indication for therapeutic-intensity
anticoagulation, the ASH guideline panel recommends dis-
continuation of heparin (strong recommendation, moderate
certainty in the evidence about effects ÅÅÅ◯).
Recommendation 2.5.b
The ASH guideline panel suggests initiation of a non-heparin
anticoagulant at therapeutic intensity (conditional recommen-
dation, moderate certainty in the evidence about effects
ÅÅÅ◯).
Recommendation 2.6
In patients with suspected HIT and a high-probability 4Ts
score, the ASH guideline panel recommends discontinuation
of heparin and initiation of a non-heparin anticoagulant at
therapeutic intensity (strong recommendation, moderate cer-
tainty in the evidence about effects ÅÅÅ◯).
Summary of the evidence. We did not find studies that
assessed the outcome of patients identified at risk of HIT
according to the 4Ts score. Instead, we modeled the clinical
outcomes on the basis of the number of patients correctly or
incorrectly identified with HIT in recommendations 2.1 and 2.2.
The effects of treatment after testing positive using the recom-
mended optimal strategy were based on the evidence for
treatments in recommendations 3.1 to 3.9. The EtD framework
is shown online at https://dbep.gradepro.org/profile/15d951fb-
5481-492e-9518-bd44091b4198.
Benefits, harms, and burden. For patients with an in-
termediate or high 4Ts score (Table 4, strategy 3), discontinuing
heparin and initiating a non-heparin anticoagulant would mean that
101 of 1000 patients (true positives) would be correctly treated,
and the risk of new or progressive thrombosis would be reduced
by 55% to 70%, but 408 of 1000 (false positives) would receive
unnecessary treatment in the short term with an attendant
increase in the risk of major bleeding. In contrast, if patients with
a low-probability 4Ts score were all treated with discontinuation of
heparin and initiation of a non-heparin anticoagulant, 9 of 1000
patients with true HIT would be treated appropriately (which is a
small benefit), but 482 patients without HIT would be unneces-
sarily exposed to a non-heparin anticoagulant with an attendant
increased risk of bleeding for a short period of time. With respect
to the use of therapeutic- or prophylactic-intensity non-heparin
anticoagulants in patients who have a high-probability 4Ts score,
there are large benefits with reductions in thrombosis when
therapeutic intensity is provided and small harms as a result of
bleeding. However, among patients who have an intermediate-
probability 4Ts score, there would be fewer people with true HIT
(ie, more false positives) and thus less benefit associated with
27 NOVEMBER 2018 x VOLUME 2, NUMBER 22 ASH 2018 VTE GUIDELINES: HIT 3373
treatment with therapeutic-intensity anticoagulation balanced
against the high risk of bleeding, particularly for patients judged
to be at high baseline bleeding risk. Conversely, with prophylactic
intensity, there may be fewer bleeds.
Other EtD criteria and considerations. When consider-
ing whether to discontinue heparin and initiate non-heparin
anticoagulants in patients with suspected HIT, the panel agreed
that some clinicians may find it unacceptable to not treat patients
suspected of HIT because of the fear of litigation. However,
clinicians may need to be reminded that treating patients with a low-
probability 4Ts score will result in more bleeds and greater costs
and only rarely prevent adverse consequences of HIT. Although
some drugs are not available in some countries, there is at least 1
non-heparin anticoagulant available in most countries.
Conclusions and research needs for this recommendation.
In patients with a high- or intermediate-probability 4Ts score, the
benefits and cost savings from preventing thrombosis outweigh
the harms (eg, bleeds) and costs of treatment. In addition, treating
for HIT is probably acceptable, feasible, and equitable. Although
the difference in cost between therapeutic- and prophylactic-
intensity therapy is negligible, in patients with an intermediate 4Ts
score who have a high risk of bleeding, there could be greater
harms with therapeutic-intensity treatment (bleeds), and the
benefits are small because most patients will not have HIT. If all
patients with a low-probability 4Ts score are treated, there may be
greater harms as a result of bleeds in a large number of patients
who do not have HIT and greater costs, and few thromboses
would be prevented in the few patients with true HIT. Research
could focus on the perceived barriers to managing patients
according to the 4Ts score.
Question: Should non-heparin anticoagulants be continued in
patients who have an intermediate or high risk of HIT according to
the 4Ts score and have a positive or negative immunoassay?
Recommendation 2.7
In patients with an intermediate-probability 4Ts score and a
negative immunoassay, the ASH guideline panel recommends
discontinuation of the non-heparin anticoagulant and re-
sumption of heparin, if indicated (strong recommendation,
moderate certainty in the evidence about effects ÅÅÅ◯).
Recommendation 2.8
In patients with a high-probability 4Ts score and a negative
immunoassay, the ASH guideline panel recommends discon-
tinuation of the non-heparin anticoagulant and resumption of
heparin, if indicated (strong recommendation, moderate cer-
tainty in the evidence about effects ÅÅÅ◯). Remark: Rarely,
patients with HIT may have a negative immunoassay, because
of a laboratory error or because the pathologic antigen involves
a complex of heparin and a molecule other than PF4. Clinical
reevaluation, a repeat immunoassay, a different immunoas-
say, and/or a functional assay may be helpful in clarifying the
diagnosis.
Recommendation 2.9
In patients with an intermediate-probability 4Ts score and a
positive immunoassay, the ASH guideline panel recommends
continued avoidance of heparin and continued administration
of a non-heparin anticoagulant at therapeutic intensity. For
those patients who were receiving prophylactic-intensity anti-
coagulation, the ASH guideline panel recommends providing
therapeutic-intensity anticoagulation (strong recommenda-
tions, moderate certainty in the evidence about effectsÅÅÅ◯).
Recommendation 2.10
In patients with a high-probability 4Ts score and a positive im-
munoassay, the ASH guideline panel recommends continued
avoidance of heparin and continued administration of a non-
heparin anticoagulant at therapeutic intensity (strong recom-
mendation, moderate certainty in the evidence about effects
ÅÅÅ◯).
Summary of the evidence. We did not find studies that
assessed clinical outcomes (eg, thrombosis, limb amputation) in
patients who were identified as being at intermediate or high risk of
HIT according to the 4Ts score and who had a positive or negative
immunoassay. Instead, we modeled the clinical outcomes on the
basis of the number of patients correctly or incorrectly identified
with HIT in recommendations 2.1 and 2.2. The effects of treatment
after testing positive using the recommended optimal strategy
(Table 4, strategy 5; Figure 1) were based on the evidence for
treatments in recommendations 3.1 to 3.9. The EtD framework
is shown online at https://dbep.gradepro.org/profile/403a664d-18cb-
4f9f-a8fe-376ee77e2b0b.
Benefits, harms, and burden. For patients who have a
high-probability 4Ts score (89 of 1000 patients) and a positive
immunoassay, continuing treatment with a non-heparin anticoag-
ulant would mean a reduction in thrombosis, death, and
amputation for 48 patients who have true HIT; however, for 6
patients without HIT, there is a short-term risk of bleeds (Table 4,
strategy 4, patients with a high-probability 4Ts score). For those
with a negative immunoassay, discontinuing treatment with a
non-heparin anticoagulant would be appropriate for 34 who do
not have HIT, but there would be harms (possible thrombosis,
amputation, or death) for the 1 patient with true HIT in whom
treatment was inappropriately stopped. For patients who had an
intermediate 4Ts score (420 of 1000 patients) and a positive
immunoassay, continuing treatment with a non-heparin anticoag-
ulant would mean that 51 who have true HIT would have a
reduction in thrombosis, amputation, or death, but 55 patients
without HIT who had continued treatment would have an increased
risk of bleeds in the short term (Table 4, strategy 4, patients with
an intermediate-probability 4Ts score). For patients who had a
negative immunoassay, discontinuing treatment with a non-heparin
anticoagulant would be appropriate for the 313 who do not have
HIT, but there would be harms (possible thrombosis, amputation,
or death) for the 1 patient with HIT in whom treatment was
inappropriately stopped.
3374 CUKER et al 27 NOVEMBER 2018 x VOLUME 2, NUMBER 22
For patients with high risk of bleeding, no other indication for
therapeutic-intensity anticoagulation, and an intermediate-probability
4Ts score who are receiving a non-heparin anticoagulant at
prophylactic intensity (per recommendation 2.4.b), changing to
therapeutic-intensity anticoagulation based on a positive immunoas-
say may be associated with small harms compared with prophylactic-
intensity treatment: 55 of 106 who have a positive immunoassay test
do not have HIT, and they may have more bleeds. However, for 51 of
106 people with HIT, the benefits would be large, because they may
have a reduced risk of thrombosis with therapeutic-intensity non-
heparin anticoagulation.
Other EtD criteria and considerations. The panel placed
greater value on preventing thrombosis or clotting than major
bleeding, and in principle, the panel valued false negatives 10 times
more than false positives (ie, the panel was willing to accept 10 false
positives for 1 false negative). The panel agreed that continuing or
discontinuing non-heparin anticoagulants is feasible, and although
some drugs are not available in some countries, there is at least 1
non-heparin anticoagulant available in most countries.
Conclusions and research needs for this recommendation.
When non-heparin anticoagulants are continued for patients with
a high- or intermediate-probability 4Ts score and a positive
immunoassay, the benefits of preventing thrombosis outweigh
the harms (eg, bleeds) and drug costs. In addition, continuing
non-heparin anticoagulants is probably acceptable, feasible,
and equitable. For patients with a high risk of bleeding, an
intermediate-probability 4Ts score, and a positive immunoassay,
the costs are negligible, and there may be large benefits from
preventing thrombosis and small harms (bleeds) when changing
from prophylactic- to therapeutic-intensity anticoagulation. The
panel identified the effect of different ELISA OD thresholds on
clinical outcomes as a research priority.
Management of the acute phase of HIT
Question: Should heparin be discontinued and a non-heparin
anticoagulant be initiated in patients with acute HITT or acute
isolated HIT?
Question: Should argatroban, bivalirudin, danaparoid, fondapar-
inux, or a DOAC be used to treat patients with acute HITT or acute
isolated HIT?
Recommendation 3.1
In patients with HITT or acute HIT without thrombosis (isolated
HIT), the ASH guideline panel recommends discontinuation of
heparin and initiation of a non-heparin anticoagulant (strong
recommendation, moderate certainty in the evidence about
effects ÅÅÅ◯). When a non-heparin anticoagulant is being
selected, the ASH guideline panel suggests argatroban, biva-
lirudin, danaparoid, fondaparinux, or a DOAC (conditional
recommendation, very low certainty in the evidence about ef-
fects Å◯◯◯). Remarks: The choice of agent may be influ-
enced by drug factors (availability, cost, ability to monitor the
anticoagulant effect, route of administration, and half-life), pa-
tient factors (kidney function, liver function, bleeding risk, and
clinical stability), and experience of the clinician. In patients with
critical illness, increased bleeding risk, or increased potential
need for urgent procedures, argatroban or bivalirudin may be
preferred because of shorter duration of effect. These patients
may require close monitoring. In patients with moderate or
severe hepatic dysfunction (Child-Pugh Class B or C), it is
advisable to avoid argatroban or use a reduced dose.
Fondaparinux and the DOACs are reasonable options in clini-
cally stable patients at average risk of bleeding. The same
contraindications to their use in the treatment of acute VTE
should be applied in determining their appropriateness for
patients with HIT.
In patients with HIT complicated by life- or limb-threatening
thromboembolism (eg, massive pulmonary embolism or venous
limb gangrene), a parenteral non-heparin anticoagulant may be
preferred, because few such patients have been treated with a
DOAC.
With respect to the choice of DOAC, most of the published
experience in HIT is with rivaroxaban. Various dosing regimens
have been reported. For patients with acute HITT, rivaroxaban
at a dose of 15 mg twice per day for 3 weeks followed by 20
mg once per day is preferred. For patients with acute isolated
HIT, rivaroxaban 15 mg twice per day until platelet count re-
covery (usually a platelet count of $150 3 109/L) followed by
20 mg once per day is preferred if there is an indication for
ongoing anticoagulation.
Summary of the evidence. We found 1 systematic review
that included 1 case series examining the discontinuation of heparin
or discontinuation of heparin and treatment with VKA and 6 studies
that compared the discontinuation of heparin and initiation of non-
heparin anticoagulants in patients with HIT.52We updated this review
and found 2 additional studies. The EtD framework is shown online at
https://dbep.gradepro.org/profile/86423A6B-5963-B7EC-ABE9-
EC0124002ED0 and https://dbep.gradepro.org/profile/5CBFE061-
894E-B073-A792-28DC54FA7F25.
One case series reported on discontinuation of heparin alone or
discontinuation of heparin and treatment with a VKA.17 One study
compared treatment with danaparoid plus warfarin vs dextran
70 plus warfarin among people with acute HIT; outcomes included
all-cause mortality, resolution of thromboembolic complications,
serious adverse events, and major bleeds.29 One study synthe-
sized 3 comparisons of treatment with lepirudin vs historical
controls among people with acute HIT; outcomes included all-
cause mortality, thromboembolic complications, and adverse
events.30 Two studies compared treatment with argatroban vs
historical controls among people with acute HIT; outcomes
included all-cause mortality, thromboembolic complications, and
adverse events.28,53 One study compared treatment with argatro-
ban, danaparoid, and fondaparinux among people with acute HIT
with regard to the outcomes of thrombosis and thrombosis-related
mortality and bleeding and bleeding-related mortality.54 One study
compared lepirudin vs fondaparinux among people with acute HIT
with regard to the outcomes of all-cause mortality, thromboembolic
complications, and adverse events.55 One case series provided
data on harms of treatment with danaparoid.56 We identified a
retrospective medical records review on the treatment of bivalirudin
in 461 suspected (n5 262), confirmed (n5 124), and remote (n5 75)
HIT patients.57 No randomized trials were identified that compared
DOACs in patients with acute HIT. We found 1 recently published
27 NOVEMBER 2018 x VOLUME 2, NUMBER 22 ASH 2018 VTE GUIDELINES: HIT 3375
systematic review of 20 studies that addressed the use of
rivaroxaban, apixaban, and dabigatran in patients with acute HIT.58
This review also provided information from a cohort of individuals
receiving DOACs after platelet count recovery. This review reported
on the outcomes of thrombosis and bleeding.
Benefits. Discontinuation of heparin and treatment with a non-
heparin anticoagulant probably results in fewer new or progressive
thrombotic events (12%-25%) than discontinuation of heparin alone
or discontinuation of heparin and treatment with a VKA (;50%). It
was uncertain whether the benefits were different among
treatments with fondaparinux, argatroban, and danaparoid.54
There were few thrombotic events reported with DOACs
(rivaroxaban, 1 of 46; apixaban, 0 of 12; dabigatran, 1 of 11),
but the number of reported patients treated with these agents
remains relatively small.
Harms and burden. Treatment with a non-heparin anticoag-
ulant likely increases major bleeds (8% to 35% rate of major
bleeds). In particular, critically ill patients and patients with certain
comorbidities may have a greater risk of bleeds.57 Limb amputations
occurred in 13.7% of patients treated with argatroban and in 4.2%
of patients treated with danaparoid.29,53 There were fewer bleeds
with DOACs (rivaroxaban, 0 of 46; apixaban, 0 of 12; dabigatran,
0 of 11). There was also very low certainty in the evidence for a
difference in the risk of bleeding with fondaparinux, argatroban, and
danaparoid because of the small number of patients included in the
study.54
Other EtD criteria and considerations. The recommen-
dation is based on greater value being placed on preventing
thrombosis than on preventing major bleeding. The panel agreed
that there is no reason that non-heparin anticoagulants would not
be prescribed or provided to any populations, and therefore there
would be no impact on equity. Starting non-heparin anticoagulants
is probably more cost-effective than stopping heparin alone,
because new or progressive thrombotic complications will be
prevented. The direct costs of the non-heparin anticoagulants are
variable in different settings and countries. The greatest cost of the
non-heparin anticoagulants that require continuous infusion (eg,
argatroban, bivalirudin, and danaparoid) may relate to prolonged
stays in the intensive care unit and hospital because of
administration and monitoring of the drug and not necessarily to
the direct cost of the medication. Fondaparinux and DOACs, which
do not require administration in a health care setting or routine
laboratory monitoring, would therefore have lower costs. However,
depending on health insurance, the costs of these agents may be a
burden to some patients. Oral medications are probably both
acceptable and feasible; however, the acceptability of a specific
medication to a clinician is likely dependent on personal experience
and would be a key factor in the choice of a specific DOAC or
parenteral non-heparin anticoagulant. Although some drugs may
not be available in some countries, there is at least 1 non-heparin
anticoagulant available in most countries.
Conclusions and research needs for this recommendation.
The benefits of discontinuing heparin and starting a non-heparin
anticoagulant (compared with discontinuing heparin alone or
discontinuing heparin and starting a VKA) may result in large
reductions in death and thrombotic events; however, harms (such
as major bleeding) may be moderate. Harms (such as major
bleeding) may be greater in critically ill patients and patients with
certain comorbidities. The benefits and harms of the effects of
DOACs compare favorably with those associated with the use of
parenteral non-heparin anticoagulants. There may be large savings
with DOACs or fondaparinux as a result of reduced hospitalization
periods. However, some patients may have to pay for the
medications, depending on health care coverage. The oral medica-
tions are probably acceptable to patients and may become
increasingly acceptable to clinicians as the evidence base and
experience grow.
More research is needed on treatment of acute HIT with DOACs,
including encouraging physicians to present outcome data when
using DOACs, creating an international registry to capture
treatment with DOACs, and conducting studies that compare
DOACs and parenteral non-heparin anticoagulants.
Question: Should a non-heparin anticoagulant at therapeutic-
intensity dosing rather than prophylactic-intensity dosing be
provided to patients with acute HITT or acute isolated HIT?
Recommendation 3.2
In patients with acute HITT or acute isolated HIT, the ASH
guideline panel recommends treatment with a non-heparin
anticoagulant at therapeutic-intensity dosing rather than
prophylactic-intensity dosing (strong recommendation, very
low certainty in the evidence about effects Å◯◯◯).
Summary of the evidence. We did not identify any
randomized controlled trials (RCTs) comparing therapeutic vs
prophylactic doses of non-heparin anticoagulants for patients with
confirmed diagnoses of acute HITT or acute isolated HIT. We
identified 2 prospective cohorts that evaluated therapeutic and
prophylactic doses of danaparoid, lepirudin (not available since
2012), and fondaparinux.59-61 These studies reported on the
outcomes of new thromboembolic events, platelet response,
mortality, major and minor bleeds, and limb amputations. The EtD
framework is shown online at https://dbep.gradepro.org/profile/
D1230F84-C07C-BBF8-9214-2AB5D71750A3.
Benefits. The study comparing danaparoid doses found that
therapeutic intensity may reduce thrombotic events by 50%;
however, this outcome is uncertain because of the small number
of patients.61 The studies comparing different doses of lepirudin
suggested no difference in thrombotic events or platelet
response.60,61 The study comparing fondaparinux doses also found
no differences in thrombotic events or mortality.59
Harms and burden. The effects on harms are uncertain
because of the small number of patients studied. An increase in bleeding
with therapeutic compared with prophylactic dosing is probable.59-61
Other EtD criteria and considerations. The panel agreed
that providing therapeutic-intensity dosing is feasible and acceptable
and that the differences in costs of prophylactic- and therapeutic-
intensity dosing would be negligible. The panel placed greater value
on preventing thrombosis and death than on the risk of major bleeding.
Conclusions and research needs for this recommendation.
The guideline panel recommends treatment with a non-heparin
anticoagulant at therapeutic-intensity dosing rather than prophylactic-
intensity dosing on the basis of very low certainty in the evidence
3376 CUKER et al 27 NOVEMBER 2018 x VOLUME 2, NUMBER 22
about effects. The strong recommendation is based on a likely large
magnitude of benefit, including prevention of more life-threatening
thrombotic events and death, and small known harm. No research
priorities related to this question were identified.
Question: Should treatment with a non-heparin anticoagulant
alone or in combination with an antiplatelet agent be provided to
patients with acute HITT or acute isolated HIT and no other
indication for antiplatelet therapy?
Recommendation 3.3
In patients with acute HITT or acute isolated HIT and no
other indication for antiplatelet therapy, the ASH guideline
panel suggests treatment with a non-heparin anticoagulant
alone rather than in combination with an antiplatelet agent
(conditional recommendation, low certainty in the evidence
about effects ÅÅ◯◯). Remark: In patients with acute HITT
or acute isolated HIT and another indication for antiplatelet
therapy (eg, coronary artery disease or recent coronary
stent placement), the decision to continue antiplatelet
therapy during treatment with a non-heparin anticoagulant
may be influenced by the risk of vascular events and
bleeding.
Summary of the evidence. We did not identify any RCTs
or non-randomized studies comparing non-heparin anticoagu-
lants alone to non-heparin anticoagulants plus antiplatelet
agents in patients with acute HITT or acute isolated HIT. We
identified 2 studies that compared heparin plus iloprost for
urgent cardiopulmonary bypass (CPB) in patients with acute
HIT with a matched control of patients without HIT.62,63 These
studies reported on the outcomes of thromboembolic events,
mortality, and bleeding. The EtD framework is shown online at
https://dbep.gradepro.org/profile/da74ffb6-d628-4392-9509-
be7652f5ab4a.
Benefits. There are no studies in patients with HIT to confirm
whether adding antiplatelet therapy to treatment with a non-
heparin anticoagulant reduces thromboembolic events.
Harms and burden. In the 2 studies of 142 patients with HIT
who received heparin plus iloprost for CPB, 30-day mortality was
reported in 9 patients, thromboembolism in 3 patients, and
moderate bleeding in 9 patients.62,63 In other populations (eg,
patients with atrial fibrillation), bleeding risk was increased with the
addition of antiplatelet therapy to anticoagulation.
Other EtD criteria and considerations. Most clinicians
and other stakeholders are likely not currently providing antiplatelet
therapy, and therefore providing a non-heparin anticoagulant alone
is probably acceptable. Although there are negligible costs
associated with adding antiplatelet therapy, adding this therapy
may increase bleeds.
Conclusions and research needs for this recommendation.
The guideline panel suggests treatment with a non-heparin
anticoagulant alone rather than in combination with an antiplatelet
agent on the basis of low certainty in the evidence. The benefits of
adding antiplatelet therapy are unknown, and there is evidence from
other populations of an increased risk of bleeding. Future research
may be needed to identify whether there are benefits of combining
antiplatelet therapy and anticoagulation among patients with HIT.
Question: Should routine insertion of an IVC filter be provided to
patients with acute HITT or acute isolated HIT?
Recommendation 3.4
In patients with acute HITT or acute isolated HIT, the ASH
guideline panel recommends against routine insertion of an
IVC filter (strong recommendation, moderate certainty in the
evidence about effects ÅÅÅ◯).
Summary of the evidence. We did not identify any
randomized or nonrandomized comparative studies that evaluated
IVC filter insertion vs no insertion in patients with acute HIT or HITT.
We found 1 case series of 10 patients with HIT who received IVC
filters that reported thrombotic events.64 We identified 1 study of 260
HIT patients receiving a different vascular intervention, CVC insertion,
in which the outcome of upper-extremity CVC-associated DVT was
reported.65 We found indirect evidence from 2 RCTs of patients
without HIT who received IVC filters in addition to anticoagulant
therapy.66,67 These trials reported on the outcomes of mortality,
pulmonary embolism, DVT, and major bleeding. The EtD framework is
shown online at https://dbep.gradepro.org/profile/306AE83F-E6BE-
7B4C-984C-211A8AB2C807.
Benefits. Indirect evidence from RCTs of patients without HIT
shows that trivial reductions in pulmonary embolisms (relative risk
[RR], 0.54; 95% confidence interval [CI], 0.22-1.33) and major
bleeding (RR, 0.81; 95% CI, 0.51-1.28) are likely with the insertion
of IVC filters.66,67 In 1000 people receiving an IVC filter, there are
likely 2 fewer pulmonary embolisms (from 4 fewer to 2 more) and 9
fewer major bleeds (from 25 fewer to 14 more). The certainty in
these effects is moderate.
Harms and burden. There are likely large harms with the
insertion of IVC filters (9 of 10 patients with acute HIT and an IVC
filter developed a new thromboembolic event).64 In addition, indirect
evidence demonstrates a risk of HIT-associated thrombosis at sites of
vascular injury. Upper-extremity DVT occurred more frequently in HIT
patients with a CVC (14 of 145 [9.7%]) than in patients without a
CVC (0 of 115 [0%]).65 The indirect evidence from RCTs of patients
without HIT is consistent, with a potential increase in mortality (RR,
1.15; 95% CI, 0.83-1.60) and new proximal DVT (RR, 1.64; 95% CI,
0.93-2.90) associated with IVC filter insertion.66,67 The evidence for
harms is of moderate certainty.
Other EtD criteria and considerations. Complications and
requirements for additional medical interventions (eg, removal of
a fractured filter) would also be increased with IVC filters.
Patients may find that insertion of IVC filters is invasive and not
acceptable.
Conclusions and research needs for this recommendation.
The guideline panel determined that there is moderate certainty in
the effects of IVC filter placement for people with HIT. Although
trivial benefits are likely with IVC filter placement, there are likely
large harms in the form of increased thromboembolic complica-
tions. Despite the feasibility of placing IVC filters, it would
probably reduce equity and not be acceptable to some patients.
Given the balance of large harms, trivial benefits, and other
27 NOVEMBER 2018 x VOLUME 2, NUMBER 22 ASH 2018 VTE GUIDELINES: HIT 3377
considerations, the guideline panel recommended against IVC
filter placement. No research priorities related to this recommen-
dation were identified.
Question: Should a VKA be initiated before platelet count recovery
in patients with acute HITT or acute isolated HIT?
Recommendation 3.5
In patients with acute HITT or acute isolated HIT, the ASH
guideline panel recommends against initiation of a VKA before
platelet count recovery (usually a platelet count of $150 3
109/L) (strong recommendation, moderate certainty in the ev-
idence about effects ÅÅÅ◯). Remark: This recommendation
also applies to patients who are taking a VKA at the onset of
acute HITT or acute isolated HITT. In these patients, the VKA
would be discontinued and intravenous vitamin K would be
administered concomitant with initiation of a non-heparin anti-
coagulant (see recommendations 3.1, 3.2, and 3.4).
Summary of the evidence. We found 3 studies of patients
with HIT who received a VKA before platelet recovery.17,68,69
One study reported on 6 patients with HIT with regard to the
outcomes of skin necrosis, limb gangrene, amputations, and
death; 1 study involved a retrospective medical record review
of patients with HIT who experienced venous limb gangrene;
and 1 study reported on the outcome of thrombosis in
21 patients with isolated HIT.68-70 The EtD framework is shown
online at https://dbep.gradepro.org/profile/2EDAF7FC-665F-302A-
97CA-ED3B70A9A133.
Benefits. There are likely no demonstrated benefits of initiating
a VKA before platelet count recovery.
Harms and burden. There are probably large harms with the
initiation of a VKA before platelet count recovery, including an
increased risk of new or progressive thrombosis and venous limb
gangrene. Among 6 patients with HIT, 5 events of skin necrosis
and 2 events of limb gangrene were reported.69 Warfarin was
withdrawn in 2 patients. One patient required limb amputation.
One patient died. Of 66 patients with HIT and DVT who received
warfarin, 8 developed venous limb gangrene.68 Of 21 patients
with HIT treated with warfarin before platelet count recovery, 10
developed thrombosis.17
Other EtD criteria and considerations. Although early
initiation of a VKA may lead to moderate savings because of earlier
hospital discharge, it may result in greater costs as a result of
thrombosis and limb loss. The cost-effectiveness probably favors
not administering a VKA before platelet recovery.
Conclusions and research needs for this recommendation.
The guideline panel determined that initiation of a VKA before
platelet count recovery is associated with trivial benefit and large
harm based on moderate certainty in the evidence about effects.
The recommendation to avoid treatment with a VKA before
platelet count recovery also applies to patients who are taking a
VKA at the onset of acute HITT or acute isolated HITT. In these
patients, the VKA would be discontinued and vitamin K would be
administered. No research priorities related to this recommenda-
tion were identified.
Question: Should routine platelet transfusion be administered in
patients with acute HITT or acute isolated HIT who are at average
risk of bleeding?
Recommendation 3.6
In patients with acute HITT or acute isolated HIT who are at
average risk of bleeding, the ASH guideline panel suggests
against routine platelet transfusion (conditional recommenda-
tion, low certainty in the evidence about effects ÅÅ◯◯).
Remark: Platelet transfusion may be an option for patients
with active bleeding or at high risk of bleeding.
Summary of the evidence. We found 4 nonrandomized
studies of patients with HIT receiving platelet transfusions. One
nationally representative inpatient database analyzed 6332 patients
with HIT International Classification of Diseases, Ninth Revision
(ICD-9) codes, of whom 450 received a platelet transfusion.71
We identified 1 retrospective cohort of 37 HIT patients, 1 cohort
of 4 HIT patients, and 1 case study of a HIT patient who received
platelet transfusions.72-74 The EtD framework is shown online at
https://dbep.gradepro.org/profile/0B5351AD-4CFF-7A8F-8E7E-
F9B9307A1441.
Benefits. There may be situations of substantial bleeding or
high risk of bleeding in which platelet transfusions would provide a
benefit to the patient. In the inpatient database study, platelet
transfusion was associated with an adjusted odds ratio (OR) for
venous thrombosis of 0.8 (95%CI, 0.4-0.7).71 In the 37-patient cohort,
no thrombotic events at 30 days were reported.72 In the 4-patient
cohort, no thrombotic events were reported.73 One HIT patient with a
positive serotonin release assay (SRA) tested SRA negative after
platelet transfusion.74
Harms and burden. There may be increased harms of
arterial thrombotic events with the addition of platelet transfusion.
In the inpatient database study, those receiving platelet transfu-
sions experienced 3.8% more arterial thromboses than patients
not receiving platelet transfusions.71 The adjusted OR for arterial
thrombosis was 3.4 (95% CI, 1.2-9.5). The adjusted OR for
venous thrombosis was 0.8 (95% CI, 0.4-0.7). The adjusted OR
for any bleeding event was 5.5 (95% CI, 2.3-12.9), although the
panel recognized that increased bleeding among patients who
received platelet transfusion was likely the result of confounding
by indication. Among the 37 HIT patients, 6 deaths were
reported.73
Other EtD criteria and considerations. Special situations
may necessitate the use of platelet transfusions. For HIT patients at
average risk of bleeding, the harms associated with routine platelet
transfusions seem to outweigh the benefits.
Conclusions and research needs for this recommendation.
The guideline panel determined that there is low certainty in the
evidence of effects against routine platelet transfusions for
people with HIT at average risk of bleeding. Platelet transfusion
may be an option for patients with active bleeding or those who
are at high risk of bleeding. No research priorities related to this
recommendation were identified.
Question: Should routine limb ultrasonography be used to screen
for asymptomatic DVT in patients with acute isolated HIT?
3378 CUKER et al 27 NOVEMBER 2018 x VOLUME 2, NUMBER 22
Recommendation 3.7.a
In patients with acute isolated HIT, the ASH guideline panel
suggests bilateral lower-extremity compression ultrasonogra-
phy to screen for asymptomatic proximal DVT (conditional
recommendation, very low certainty in the evidence about ef-
fects Å◯◯◯).
Recommendation 3.7.b
In patients with acute isolated HIT and an upper-extremity CVC,
the ASH guideline panel suggests upper-extremity ultraso-
nography in the limb with a catheter to screen for asymptomatic
DVT. The ASH guideline panel suggests against upper-
extremity ultrasonography in limbs without CVCs to screen
for asymptomatic DVT (conditional recommendations, very low
certainty in the evidence about effects Å◯◯◯). Remark:
These recommendations do not apply to patients with signs or
symptoms suggestive of DVT in whom diagnostic imaging
would be indicated.
Summary of the evidence. We found 5 nonrandomized
studies that reported on DVT outcomes in patients with confirmed
HIT.17,19,65,75,76 Three cohort studies reported on symptomatic lower-
extremity proximal DVT.17,19,75 One study reported on symptomatic
upper-extremity DVT.19 Two cohort studies reported on asymptomatic
HIT patients who were screened for silent DVT.65,76 The EtD
framework is shown online at https://dbep.gradepro.org/profile/
52FE6F09-0233-F65B-BA7A-5ADB96E1007D.
Benefits. There may be benefits of screening for silent DVTs
when the findings would change clinical practice; however, this is
uncertain. Ultrasound studies identified silent lower-extremity DVT
in 12% to 44% of asymptomatic HIT patients.65,76 The panel
agreed that the benefits of lower-extremity screening in patients
with acute isolated HIT are moderate because of the high
prevalence of silent DVT and the high risk of pulmonary embolism
with proximal DVT.
Although no study reported on the prevalence of silent upper-
extremity DVT among people with HIT, symptomatic upper-extremity
DVT is common in HIT patients with a CVC (14 of 145) and
uncommon in those without a CVC (0 of 115).65 The panel agreed
that there may be benefit to screening patients with CVC for upper-
extremity DVT in the limb where the CVC has been placed because
of the high baseline prevalence of CVC-associated upper-extremity
DVT and the moderate risk of pulmonary embolism associated with
upper-extremity DVT. The panel agreed that the benefit of screening
for upper extremity DVT in the absence of a CVC is likely to be trivial
because of the low baseline prevalence of symptomatic DVT.
Harms and burden. There may be harms of unnecessary
treatment, such as major bleeds, with the detection and treatment
of silent DVT for both upper and lower extremities, but this is
uncertain.
Other EtD criteria and considerations. The cost of
ultrasound screening is negligible given the restricted patient
population (ie, patients with acute isolated HIT), and the screening
is probably cost-effective with regard to screening for lower-
extremity DVT or upper-extremity CVC-associated DVT. Ultrasound
is probably not cost-effective for upper-extremity DVT screening in
the absence of a CVC.
Conclusions and research needs for this recommendation.
The guideline panel determined that there is very low certainty
in the evidence of effects for bilateral lower-extremity com-
pression ultrasonography to screen for asymptomatic DVT. The
guideline panel determined that there is very low certainty in the
evidence of effects for upper-extremity ultrasonography to
screen for CVC-associated DVT. The guideline panel de-
termined that there is very low certainty in the evidence of
effects for upper-extremity ultrasonography to screen for DVT
in the absence of a CVC.
Research is needed to determine whether a strategy of screening
and treatment of asymptomatic DVT in patients with acute isolated
HIT influences outcomes important to patients such as symptom-
atic thromboembolism, major bleeding, and death.
Question: Should anticoagulation be continued until platelet
count recovery or for a longer period of time in patients with
acute isolated HIT and no asymptomatic DVT by screening
ultrasonography?
Recommendation 3.8
In patients with acute isolated HIT and no asymptomatic DVT
identified by screening compression ultrasonography, the ASH
guideline panel suggests that anticoagulation be continued, at
a minimum, until platelet count recovery (usually a platelet
count of $150 3 109/L). The ASH guideline panel suggests
against continuing treatment of $3 months unless the patient
has persisting HIT without platelet count recovery (conditional
recommendations, very low certainty in the evidence Å◯◯◯).
Remark: These recommendations apply only to patients with
isolated HIT. The ASH guideline panel did not address the
duration of anticoagulation in patients with acute HITT and no
other indication for anticoagulation in whom anticoagulation is
typically given for 3 to 6 months.
Summary of the evidence. We found 1 cohort study that
followed the progression of platelet counts and thrombotic events
of 62 untreated patients with isolated HIT.17 The EtD framework is
shown online at https://dbep.gradepro.org/profile/154EF022-
9F75-AB97-A89A-1B0CFABAF906.
Benefits. The cohort study found that thromboembolic events
occurred in 52% of patients within 30 days after discontinuation of
heparin. Most events occurred within the first 10 days, correspond-
ing to the period of platelet count recovery. There may be an
additional benefit of prolonged treatment beyond platelet count
recovery, but this is uncertain.
Harms and burden. The cumulative risk of bleeding with
anticoagulant therapy increases with treatment duration.
Other EtD criteria and considerations. The costs of
treatment beyond platelet count recovery are likely to be negligible
because the patient would be transitioned to an oral agent, and oral
anticoagulants are relatively inexpensive. However, the costs of
27 NOVEMBER 2018 x VOLUME 2, NUMBER 22 ASH 2018 VTE GUIDELINES: HIT 3379
increased bleeds with extended anticoagulant therapy may out-
weigh reduction in thromboembolic events, thus potentially favoring
a shorter course of treatment.
Conclusions and research needs for this recommendation.
The guideline panel determined that there is evidence of high
thrombotic risk in patients with isolated HIT during the period of
platelet count recovery. The benefits of a longer course of treatment
are trivial (as a result of a low risk of thromboembolic events after
platelet recovery), and the harms (cumulative risk of bleeding) with
greater (but limited) duration of therapy are small. Although some
clinicians provide treatment of 4 to 6 weeks, the panel could not
agree on a specific duration of therapy on the basis of current
evidence and therefore provided a minimum (until platelet count
recovery) and maximum (,3 months) duration of treatment. The
panel agreed that studies comparing different lengths of therapy
would be useful for determining the optimal duration of treatment in
patients with isolated HIT.
Question: Should a DOAC (eg, dabigatran, rivaroxaban, or
apixaban) rather than a VKA be provided to patients with subacute
HIT A?
Recommendation 3.9
In patients with subacute HIT A, the ASH guideline panel
suggests treatment with a DOAC (eg, dabigatran, rivaroxaban,
or apixaban) rather than a VKA (conditional recommendation,
moderate certainty in the evidence about effects ÅÅÅ◯).
Remarks: The choice of agent may be influenced by drug
factors (availability, cost, ability to monitor the anticoagulant ef-
fect, route of administration, and half-life), patient factors (kidney
function, liver function, bleeding risk, and clinical stability), and
experience of the clinician.
DOACs are preferred in clinically stable patients at average risk
of bleeding. The same contraindications to their use in the
treatment of acute VTE should be applied in determining their
appropriateness for patients with HIT.
Summary of the evidence. We found a systematic review
of case series of 11 patients with HIT who received DOACs after
platelet count recovery.58 The systematic review reported on
outcomes of thrombotic events and major bleeding. Indirect evidence
comparing DOACs with a VKA in patients with VTE (without HIT) was
also used to inform this recommendation. The EtD framework is shown
online at https://dbep.gradepro.org/profile/39E8D89A-A33A-28E1-
B5F9-809F7FB7BA27.
Benefits. Indirect evidence in patients with VTE (without HIT)
shows that DOACs likely lead to a lower risk of bleeding than a VKA
and to a risk of thrombotic events similar to that associated with a
VKA.77 Among 11 patients with HIT who were transitioned to
DOACs after platelet count recovery, there were no thrombotic
events.58
Harms and burden. Indirect evidence in patients with VTE
(without HIT) shows that there are likely fewer bleeds with DOACs
than with a VKA. Among 11 patients with probable HIT who were
transitioned to DOACs, 1 patient had a major hemorrhage
secondary to known varices.58
Other EtD criteria and considerations. DOACs are more
expensive than VKAs. Out-of-pocket costs for patients will depend
on insurance coverage. The potential greater out-of-pocket costs of
DOACs may reduce equity. However, VKAs come with additional
costs, including those associated with prolonged hospitalization
and monitoring. DOACs may be more acceptable to patients
because they do not require routine laboratory monitoring and
dietary restrictions.
Conclusions and research needs for this recommendation.
The guideline panel suggests treatment with a DOAC rather than a
VKA for patients with subacute HIT A based on moderate certainty
in the evidence of effects. The particular choice of agent may be
influenced by drug factors (availability, cost, ability to monitor the
anticoagulant effect, route of administration, and half-life), patient
factors (kidney function, liver function, bleeding risk, and clinical
stability), and experience of the clinician. The panel agreed that an
international registry of patients with subacute HIT A treated with a
DOAC would provide important information.
Cardiovascular surgery
Question: Should intraoperative anticoagulation with (1) heparin or
(2) treatment with a non-heparin anticoagulant or (3) plasma
exchange and heparin or (4) heparin and an antiplatelet agent be
provided to patients with acute HIT or subacute HIT A who require
cardiovascular surgery?
Good practice statement 4.1.a
In patients with acute HIT or subacute HIT A who require
cardiovascular surgery, the ASH guideline panel agrees that
surgery should be delayed until the patient has subacute HIT B
or remote HIT (see recommendation 4.2), if feasible.
Recommendation 4.1.b
If delaying surgery is not feasible, the ASH guideline panel
suggests one of the following: intraoperative anticoagulation
with bivalirudin, intraoperative heparin after treatment with
preoperative and/or intraoperative plasma exchange, or
intraoperative heparin in combination with a potent anti-
platelet agent (eg, prostacyclin analog or tirofiban) (condi-
tional recommendation, low certainty in the evidence about
effects ÅÅ◯◯). Remarks: The choice of strategy may be
influenced by availability, cost, and clinician experience.
Consensus protocols for the plasma exchange and intra-
operative heparin strategy and for the intraoperative heparin
and potent antiplatelet agent strategy have not been estab-
lished. If either of these strategies is used, treatment with
heparin is limited to the intraoperative setting and avoided
before and after surgery.
Summary of the evidence. We did not identify any RCTs
comparing non-heparin anticoagulants, preoperative or intraoper-
ative plasma exchange with heparin, or heparin and an antiplatelet
agent for use in patients with acute HIT or subacute HIT A. No
nonrandomized comparison studies of interventions were identified.
3380 CUKER et al 27 NOVEMBER 2018 x VOLUME 2, NUMBER 22
We identified 2 prospective cohort studies, 1 case series, 1 case
report of a single patient with HIT, and indirect evidence in the
form of small randomized trials in patients without HIT who
received a non-heparin anticoagulant (ie, bivalirudin, danaparoid, and
argatroban).78-80 The 3 studies conducted among patients with
HIT reported on outcomes of procedural success, mortality, and
major bleeding. One systematic review reported on 10 studies of
12 patients with acute HIT who received bivalirudin during
cardiovascular surgery.81 The systematic review reported on
outcomes of bleeding and adverse events. Indirect evidence
among patients without HIT treated with bivalirudin vs heparin
undergoing cardiovascular surgery reported on the outcomes of
procedural success, myocardial infarction, stroke, major bleeding,
and mortality.82-85 Indirect evidence among patients without HIT
treated with danaparoid vs heparin undergoing cardiovascular
surgery reported on the outcomes of myocardial infarction,
reoperation for bleeding, and mortality.86,87
We identified 4 studies that reported on cases of patients with
acute HIT undergoing cardiovascular surgery who were treated with
heparin and plasma exchange.88-91 These studies reported on the
outcomes of HIT-related thrombosis, mortality, amputation, and
other adverse events.
We identified 6 studies that reported on cases of patients with HIT
undergoing cardiovascular surgery who were treated with heparin
and antiplatelet agents, specifically, prostacyclin analogs or
tirofiban.62,63,92-95 These studies reported on the outcomes of
thrombotic events, bleeding, and adverse events. The EtD
framework is shown online at https://dbep.gradepro.org/profile/
5A998D17-1484-A5FC-ABD7-D817503963DC.
Benefits. For patients with HIT undergoing cardiovascular
surgery, thrombotic events and procedural success may be similar
across interventions and comparators (ie, non-heparin anticoagu-
lants, heparin with plasma exchange, and heparin with potent
antiplatelet agents), but this is uncertain because there are no direct
comparisons. The 3 studies of patients with HIT who received
bivalirudin for either on-pump or off-pump surgery reported rates of
94% and 92% for procedural success (defined as absence of
death, Q-wave myocardial infarction, repeat operation for coronary
revascularization, or stroke), 4 deaths (n 5 155), and no major
bleeds.78-80
Harms and burden. For patients with HIT undergoing
cardiovascular surgery, the risk of bleeding may be similar across
treatment options, but this is uncertain. However, treatment with
danaparoid may increase the risk of bleeding. In 1 case series of 4
patients treated with danaparoid during CPB, all 4 experienced
blood loss requiring transfusion.92 In addition, the panel agreed that
the half-life of danaparoid and fondaparinux is inappropriately long
for cardiac surgery and may therefore lead to increased risk of
bleeding. Certain antiplatelet agents (eg, iloprost) may have
additional harms, such as hypotension. Plasma exchange also
carries potential harms, including procedural risk and adverse
effects associated with receipt of donor plasma.
Other EtD criteria and considerations. Costs, availability,
and clinical experience may vary with each treatment strategy.
Conclusions and research needs for this recommendation.
The guideline panel recommended delaying cardiovascular
surgery until the patient has subacute HIT B or remote HIT so
that intraoperative heparin can be used. However, if delaying
surgery is not feasible, the panel determined that there is very low
certainty in the evidence of effects for treatment with intraoperative
anticoagulation with bivalirudin, for preoperative and/or intraoper-
ative plasma exchange and heparin, and for treatment with heparin
and a potent antiplatelet agent such as a prostacyclin analog or
tirofiban. The benefits and harms of these options may be similar.
Among non-heparin anticoagulants, there is more evidence and
experience with bivalirudin than other agents. There may be more
bleeding with danaparoid. Costs, availability, and clinical experience
may vary with each treatment strategy.
Direct comparison of treatment options for intraoperative anti-
coagulation in patients with HIT is an important research priority.
Anticoagulation in HIT patients with ventricular assist devices or
those who use extracorporeal membrane oxygenation is also worthy
of investigation.
Question: Should intraoperative anticoagulation with heparin or
treatment with a non-heparin anticoagulant or plasma exchange
and heparin or heparin and an antiplatelet agent be provided to
patients with subacute HIT B or remote HIT who require
cardiovascular surgery?
Recommendation 4.2
In patients with subacute HIT B or remote HIT who require
cardiovascular surgery, the ASH guideline panel suggests
intraoperative anticoagulation with heparin rather than treat-
ment with a non-heparin anticoagulant, plasma exchange and
heparin, or heparin combined with an antiplatelet agent (con-
ditional recommendation, very low certainty in the evidence
about effects Å◯◯◯). Remarks: Treatment with heparin
would be limited to the intraoperative setting and avoided be-
fore and after surgery. Postoperative platelet count monitoring
for HIT may be necessary, even when postoperative heparin is
not given, because delayed-onset (autoimmune) HIT beginning
5 to 10 days after the intraoperative heparin exposure has been
reported.
Summary of the evidence. We did not identify any RCTs
comparing non-heparin anticoagulants, plasma exchange with
heparin, or heparin and an antiplatelet agent for use in patients
with subacute HIT B or remote HIT. No nonrandomized comparison
studies of interventions were identified.
We identified 10 studies that reported patients with subacute HIT B
or remote HIT requiring cardiovascular interventions who received
heparin, non-heparin anticoagulants, antiplatelet agents, or plasma
exchange.39,96-104 The studies reported on outcomes of thrombotic
events, bleeding, adverse events, mortality, and recurrent HIT. The
EtD framework is shown online at https://dbep.gradepro.org/
profile/DA1DC8AA-C703-3D20-8DEC-32208503CEED.
Benefits. Six studies reported on 39 patients with subacute
HIT B or remote HIT undergoing cardiovascular surgery who
received intraoperative heparin.39,96-100 Among the sixteen
patients with subacute HIT B, no thrombotic events were
reported.96,98,100 Among the 23 patients with remote HIT, no
new thrombotic events were reported.39,97,99,100
27 NOVEMBER 2018 x VOLUME 2, NUMBER 22 ASH 2018 VTE GUIDELINES: HIT 3381
Two studies reported on 2 patients undergoing cardiovascular
surgery with remote HIT who received non-heparin anticoagulants
(bivalirudin and danaparoid).101,102 No events were reported for the
patient treated with bivalirudin.101 The patient treated with
danaparoid developed thrombosis of the CPB circuit.88
Two studies reported on 8 patients with remote HIT undergoing
cardiovascular surgery who received antiplatelet agents.103,104
No thrombotic events or deaths were reported. One study
reported on 6 patients with subacute HIT B who received
antiplatelet agents.104 No thrombotic events or deaths were
reported.
One study reported on 1 patient undergoing cardiovascular surgery
who was treated with plasma exchange until antibody clearance,
and heparin was used during CPB.105 No events were reported.
Harms and burden. For patients with subacute HIT B or
remote HIT undergoing cardiovascular surgery, the risk of re-
currence of acute HIT may be low with all interventions, but this is
uncertain. There may be greater risk of bleeding with treatments
other than heparin. The risk of bleeding is likely to be lower with
heparin than with a non-heparin anticoagulant or with heparin and
an antiplatelet agent, in part because of greater familiarity with
heparin dosing and monitoring. Heparin-associated bleeding may
be easier to manage because of the availability of a reversal agent
(protamine). Antiplatelet agents may have additional harms, such as
hypotension with iloprost. Plasma exchange carries additional
harms, including procedural risk and adverse effects associated
with receipt of donor plasma.
Six studies reported on 39 patients with subacute HIT B or remote HIT
undergoing cardiovascular surgery who received heparin.39,96-100 For
the 23 patients with remote HIT, 1 case of recurrent HIT and 1 case of
severe bleeding were reported.39,97,99,100
Two studies reported on 2 patients undergoing cardiovascular
surgery with remote HIT who received non-heparin anticoagulants
(bivalirudin and danaparoid).101,102 The patient who received
danaparoid developed thrombosis of the CPB circuit, sepsis,
respiratory failure, pancreatitis, and renal failure but made a full
recovery.102
Two studies reported on 8 patients with remote HIT who received
heparin with an antiplatelet agent. One bleeding event leading to
reoperation was reported.103,104 One study reported on 6 patients
with subacute HIT B who received heparin with an antiplatelet
agent.104 Three events of bleeding leading to reoperation were
reported.
Other EtD criteria and considerations. There are addi-
tional costs and possible adverse events associated with using a
non-heparin anticoagulant, preoperative plasma exchange and
heparin, or heparin and an antiplatelet agent; adverse events
include bleeding and hypotension and the procedural risk and
adverse effects of receiving donor plasma.
Conclusions and research needs for this recommendation.
The guideline panel suggests intraoperative anticoagulation with
heparin rather than treatment with a non-heparin anticoagulant,
plasma exchange and heparin, or heparin and an antiplatelet agent
on the basis of very low certainty in the evidence of effects.
Heparin is the standard of care for cardiovascular surgery and has
several advantages in this context, including familiarity, measur-
ability, and reversibility. However, there was very low-quality
evidence of the risk of recurrence of HIT when heparin is used.
There are additional costs and possible adverse events associated
with using a non-heparin anticoagulant, plasma exchange and
heparin, or heparin and an antiplatelet agent. Overall, the desirable
consequences of using heparin and the undesirable conse-
quences of using the other treatment strategies probably favor
use of heparin.
Research priorities include development of a registry on the use of
heparin during cardiac surgery among patients with subacute HIT B
or remote HIT.
Percutaneous cardiovascular intervention
Question: Should bivalirudin, argatroban, danaparoid, or fondapar-
inux be provided to patients with acute HIT or subacute HIT A who
require PCI?
Recommendation 5.1
In patients with acute HIT or subacute HIT A who require PCI,
the ASH guideline panel suggests treatment with bivalirudin
rather than a different non-heparin anticoagulant (conditional
recommendation, low certainty in the evidence ÅÅ◯◯).
Remarks: If bivalirudin is not available or there is a lack of
institutional experience, argatroban might be a suitable sub-
stitute. The choice of drug may be influenced by drug avail-
ability, cost, ability to monitor the anticoagulant effect, and
clinician experience.
Summary of the evidence. We did not identify any RCTs
comparing different non-heparin anticoagulants for use during PCI
in patients with acute HIT or subacute HIT A. We identified 3
studies evaluating the use of non-heparin anticoagulants (bivalirudin
and argatroban) during PCI among patients with suspected or
confirmed HIT.56,106,107 These studies reported on the outcomes of
mortality and bleeding. We identified 2 studies reporting indirect
evidence on treatment with non-heparin anticoagulants during PCI
among patients without HIT.108,109 These studies reported on the
outcomes of bleeding, ischemic adverse events, and composite
outcomes of death, myocardial infarction, or urgent revasculariza-
tion. The EtD framework is shown online at https://dbep.gradepro.
org/profile/8BC628BF-6464-8F9C-A540-E848F59ACFB0.
Benefits. Among 91 patients with HIT, suspected HIT, or
remote HIT treated with argatroban during PCI, no deaths were
reported.107 For 61 PCI procedures in which danaparoid was used,
no adverse outcomes were reported.56 Among 19 772 patients
without HIT, bivalirudin demonstrated a lower risk of major bleeding
than heparin (OR, 0.55; 95% CI, 0.44-0.69) and a similar risk of
ischemic adverse events (OR, 1.07; 95% CI, 0.96-1.19).108
Harms. For patients with HIT undergoing PCI, there is
concern that non-heparin anticoagulants could increase bleeding
compared with heparin (although this was not observed in a meta-
analysis comparing UFH and bivalirudin in patients without HIT).
Among 50 patients with suspected or confirmed HIT receiving
bivalirudin, 1 death and 1 bleeding event were reported.106 Among
91 patients with suspected or confirmed HIT who received
argatroban, 1 bleeding event was reported.107 Among 152 patients
without HIT who received argatroban or abciximab or eptifibatide
3382 CUKER et al 27 NOVEMBER 2018 x VOLUME 2, NUMBER 22
during PCI, 4 composite outcomes of death, myocardial infarction,
or urgent revascularization (no deaths, 4 myocardial infarctions, and
2 revascularizations) and 2 major bleeds were reported at 30
days.109
Other EtD criteria and considerations. Clinicians have
more experience in treating patients without HIT with bivalirudin
during PCI.
Conclusions and research needs for this recommendation.
The guideline panel suggests treatment with bivalirudin during PCI
for patients with acute HIT or subacute HIT A on the basis of low
certainty in the evidence about effects. This recommendation is
based primarily on favorable evidence and extensive experience
with bivalirudin in patients without HIT. If bivalirudin is not available
or there is a lack of institutional experience, argatroban might be a
suitable substitute. The choice of drug may be influenced by drug
availability, cost, ability to monitor the anticoagulant effect, and
clinician experience. There was much less data on the use of
bivalirudin, argatroban, or other non-heparin anticoagulants in
patients with HIT. No research priorities related to this recommen-
dation were identified.
Question: Should bivalirudin, argatroban, danaparoid, fondapar-
inux, or heparin be provided to patients with subacute HIT B or
remote HIT who require PCI?
Recommendation 5.2
In patients with subacute HIT B or remote HIT who require PCI,
the ASH guideline panel suggests treatment with bivalirudin
rather than UFH (conditional recommendation, very low cer-
tainty in the evidence Å◯◯◯).
Remarks: Heparin is an acceptable alternative for patients with
subacute HIT B or remote HIT if a suitable non-heparin antico-
agulant is not available or clinician experience is lacking. If heparin
is used, exposure should be limited to the intraprocedural setting
and should be avoided before and after the procedure.
If bivalirudin is not available or if there is a lack of institutional
experience, argatroban might be a suitable substitute. Choice
of drug may be influenced by drug availability, cost, ability to
monitor the anticoagulant effect, and clinician experience.
Summary of the evidence. We did not identify any RCTs
comparing non-heparin anticoagulants and UFH for use in patients
with subacute HIT B or remote HIT who require PCI. We identified 1
case study that reported on the use of danaparoid for a patient with
remote HIT requiring PCI.110 This study reported on the outcomes
of thrombotic and bleeding events. Two studies reported indirect
evidence of treatment with non-heparin anticoagulants during PCI
among patients without HIT.108,109 These studies reported on the
outcomes of bleeding, ischemic adverse events, mortality, myocar-
dial infarction, and urgent revascularization. Two studies reported
indirect evidence of treatment with non-heparin anticoagulants
(bivalirudin and danaparoid) among people with subacute HIT B
and remote HIT undergoing cardiac surgery.101,102 These studies
reported on the outcomes of transfusions and adverse events. Six
studies reported indirect evidence of treatment with heparin among
people with subacute HIT B and remote HIT undergoing
cardiac surgery.39,96-100 These studies reported on the outcomes
of thrombotic and bleeding events and recurrent HIT. The EtD
framework is shown online at https://dbep.gradepro.org/profile/
505C2564-BBEA-0CCE-BB2D-5D3961D8CAD4.
Benefits. There may be benefits among patients with sub-
acute HIT B or remote HIT undergoing PCI who are treated with
non-heparin anticoagulants. In 1 patient with remote HIT un-
dergoing PCI who received danaparoid, no thrombotic or bleeding
events were reported. Among 19 772 patients without HIT
undergoing PCI, bivalirudin demonstrated a lower risk of major
bleeding than heparin (OR, 0.55; 95% CI, 0.44-0.69) and a similar
risk of ischemic adverse events (OR, 1.07; 95% CI, 0.96-1.19).108
Among 152 patients without HIT undergoing PCI, 4 composite
outcomes of death, myocardial infarction, or urgent revasculariza-
tion (no deaths, 4 myocardial infarctions, and 2 revascularizations)
and 2 major bleeds were reported at 30 days.109 For 16 patients
with subacute HIT B undergoing CPB who received heparin, no
thrombotic events were reported. Among 23 patients with remote
HIT undergoing CPB who received heparin, 1 case of recurrent HIT
was reported; however, no other thrombotic events were
reported.39,97,99,100
Harms. There may be harms from treatment with non-heparin
anticoagulants for patients with subacute HIT B or remote HIT
undergoing PCI, but this is uncertain. One patient with remote HIT
undergoing CPB who received bivalirudin required red blood cell
and fresh frozen plasma transfusions, but no other outcomes were
reported.101 One patient with remote HIT undergoing CPB who
received danaparoid developed thrombosis of the CPB circuit,
sepsis, respiratory failure, pancreatitis, and renal failure but made
a full recovery.102 Among 23 patients with remote HIT un-
dergoing CPB who received heparin, 1 case of severe bleeding
was reported.39,97,99,100
Other EtD criteria and considerations. Alternative anti-
coagulants probably require specialized clinical experience.
Bivalirudin is widely used for PCI in the United States but not
internationally. Heparin could be used in areas where alterna-
tive non-heparin anticoagulants are unavailable or clinical
staff are unfamiliar with treating patients with non-heparin
anticoagulants.
Conclusions and research needs for this recommendation.
The guideline panel suggests treatment with bivalirudin rather
than unfractionated heparin for patients with subacute HIT B or
remote HIT requiring PCI on the basis of low certainty in the
evidence of effects. This recommendation is based on evidence
that bivalirudin reduces bleeding risk compared with heparin in
patients without HIT and that use of a non-heparin anticoag-
ulant may avoid the small risk of HIT recurrence with use of
heparin. Heparin is an acceptable alternative in patients with
subacute HIT B or remote HIT if a suitable non-heparin
anticoagulant is not available or clinician experience is lacking.
If heparin is used, exposure should be limited to the intra-
procedural setting and should be avoided before and after the
procedure. If bivalirudin is not available or there is a lack of
institutional experience, argatroban might be a suitable sub-
stitute. The choice of drug may be influenced by drug availability,
cost, ability to monitor the anticoagulant effect, and clinician
experience. No research questions related to this recommendation
were identified.
27 NOVEMBER 2018 x VOLUME 2, NUMBER 22 ASH 2018 VTE GUIDELINES: HIT 3383
Renal replacement therapy
Question: Should argatroban, danaparoid, bivalirudin, fondapar-
inux, or a DOAC be provided to patients with acute HIT who are
receiving renal replacement therapy and require anticoagulation to
prevent thrombosis of the dialysis circuitry?
Recommendation 6.1
In patients with acute HIT who are receiving renal replacement
therapy and require anticoagulation to prevent thrombosis of
the dialysis circuitry, the ASH guideline panel suggests treat-
ment with argatroban, danaparoid, or bivalirudin rather than
other non-heparin anticoagulants (conditional recommenda-
tion; very low certainty in the evidence about effects Å◯◯◯).
Remark: The choice of agent may be influenced by drug
factors (availability and cost), patient factors (liver function),
and experience of the clinician.
Summary of the evidence. We did not identify any RCTs
comparing non-heparin anticoagulants for use in patients with
acute HIT who require renal replacement therapy. We identified
nonrandomized studies evaluating the use of argatroban, danapa-
roid, fondaparinux, bivalirudin, and rivaroxaban. Ten studies
reported on treatment with argatroban,111-120 3 studies reported
on treatment with danaparoid,70,121,122 3 studies reported on
treatment with fondaparinux,123-125 2 studies reported on
treatment with bivalirudin,57,126 and 1 study reported on treatment
with rivaroxaban.127 These studies reported on the outcomes of
bleeding, thromboembolic events, mortality, and serious adverse
events.
Indirect evidence was identified on the use of argatroban and
danaparoid among patients without HIT. One RCT evaluated 13
patients with end-stage renal disease without HIT who received
argatroban during intermittent hemodialysis.128 Two RCTs com-
pared danaparoid and heparin or LMWH during hemodialysis in
patients without HIT.129,130 These studies reported on the
outcomes of bleeding, thromboembolic events, serious adverse
events, and laboratory measures. The EtD framework is shown
online at https://dbep.gradepro.org/profile/948a7b63-bf96-41ec-
8e18-ae25298b9836.
Benefits. There may be moderate benefits associated with
the treatment of patients with HIT undergoing renal replacement
therapy with selected non-heparin anticoagulants (eg, argatroban,
danaparoid, or bivalirudin) compared with others (eg, fondaparinux
and rivaroxaban) for which there is little data and greater
dependence on the kidneys for clearance. Among 13 patients
without HIT who received argatroban, no thrombosis, bleeding,
serious adverse events, or clinically significant changes in vital
signs or routine laboratory measures were reported.128 Among 62
patients without HIT who received danaparoid, no events were
reported.129,130 Among 9 patients with HIT who received fondapar-
inux, no bleeding or other adverse events were reported.123-125
Among 114 patients with HIT who received bivalirudin during
dialysis, no amputations were reported, 7 had new thrombo-
embolic events, and 32 died.57,126 For the 1 patient who
received rivaroxaban, no thromboembolic or bleeding events
were reported.127
Harms and burden. Among 97 patients with HIT who
received argatroban, 18 deaths were reported; however, none
were the result of thrombosis.111-120 One patient with peripheral
vascular disease underwent amputation, and 3 patients developed
thrombotic events. Major bleeding occurred in 3 of 50 treatment
courses in 1 study and in 2 of 30 patients in another study. One
patient required co-intervention with aspirin. Among 115 patients
with HIT receiving danaparoid during hemodialysis, 8 patients
developed nonfatal thromboembolic events (of which 2 required
amputation), 28 died, 11 had nonfatal major bleeding events, 7 had
minor bleeding events, 11 had nonfatal adverse events, and 14 had
fatal adverse events.70,121,122 Among 9 patients with HIT who
received fondaparinux, 3 patients developed thromboses that were
managed by increasing the dose.123-125 Among 114 patients with
HIT who received bivalirudin during dialysis, 13 experienced major
bleeding events.57,126
Other EtD criteria and considerations. Compared with
fondaparinux and rivaroxaban, argatroban, danaparoid, and bivalir-
udin are less dependent on the kidneys for clearance. Non-heparin
anticoagulants are probably feasible to provide. However, there may
be some jurisdictions in which specific non-heparin anticoagulants
are not available. At least 1 non-heparin anticoagulant is probably
available, acceptable, and feasible to provide in most jurisdictions.
Conclusions and research needs for this recommendation.
The guideline panel suggests treatment with argatroban, danapa-
roid, or bivalirudin rather than other non-heparin anticoagulants on
the basis of very low certainty in the evidence of effects. The
choice of agent may be influenced by drug factors (availability and
cost), patient factors (liver function), and experience of the
clinician. There may be moderate benefits with select non-
heparin anticoagulants (such as argatroban, danaparoid, or
bivalirudin) compared with others (such as fondaparinux and
rivaroxaban) for which there is little data and greater dependence
on the kidneys for clearance. No research questions related to this
recommendation were identified.
Question: Should argatroban, danaparoid, bivalirudin, fondapar-
inux, regional citrate, heparin, or a DOAC be provided to patients
with subacute HIT A, subacute HIT B, or remote HIT who are
receiving renal replacement therapy, are not otherwise receiving
anticoagulation, and require anticoagulation to prevent thrombosis
of the dialysis circuit?
Recommendation 6.2
In patients with subacute HIT A, subacute HIT B, or remote
HIT who are receiving renal replacement therapy, are not
otherwise receiving anticoagulation, and require anti-
coagulation to prevent thrombosis of the dialysis circuit, the
ASH guideline panel suggests regional citrate rather than
heparin or other non-heparin anticoagulants (conditional rec-
ommendation; very low certainty in the evidence about effects
Å◯◯◯). Remark: Citrate is not appropriate for patients with
acute HIT who require systemic rather than regional anti-
coagulation (see recommendation 6.1).
Summary of the evidence. We did not identify any RCTs
comparing non-heparin anticoagulants for use in patients with
3384 CUKER et al 27 NOVEMBER 2018 x VOLUME 2, NUMBER 22
subacute HIT A, subacute HIT B, or remote HIT who require renal
replacement therapy. We identified nonrandomized studies evaluating
the use of argatroban, danaparoid, fondaparinux, bivalirudin, and
rivaroxaban. Ten studies reported on treatment with argatroban,111-120
3 studies reported on treatment with danaparoid,70,121,122 3 studies
reported on treatment with fondaparinux,123-125 2 studies reported on
treatment with bivalirudin,57,126 and 1 study reported on treatment
with rivaroxaban.127 These studies reported on the outcomes of
bleeding, thromboembolic events, mortality, and serious adverse
events.
Indirect evidence was identified on the use of argatroban and
danaparoid among patients without HIT. One RCT evaluated 13
patients with end-stage renal disease without HIT who received
argatroban during intermittent hemodialysis.128 Two RCTs com-
pared danaparoid and heparin or LMWH during hemodialysis in
patients without HIT.129,130 One systematic review evaluated 14
RCTs comparing regional citrate to heparin for patients without HIT
who required continuous renal replacement therapy.131 One case
series reported on 3 patients with remote HIT who received a
second course of heparin for various indications more than 100
days after the initial episode of HIT.39 These studies reported on the
outcomes of bleeding, thromboembolic events, serious adverse
events, and laboratory measures. The EtD framework is shown
online at https://dbep.gradepro.org/profile/1553EA74-7DB0-
1209-84EB-DF6DBC3DA805.
Benefits. Patients with HIT and end-stage renal disease may
benefit from treatment with argatroban, danaparoid, bivalirudin, or
citrate, but the relative benefits are uncertain. Among 13 patients
without HIT who received argatroban, no thrombosis, bleeding,
serious adverse events, or clinically significant changes in vital signs
or routine laboratory measures were reported.128 Among 62
patients without HIT who received danaparoid, no events were
reported.129,130 Among 9 patients with HIT who received fondapar-
inux, no bleeding or other adverse events were reported.123-125
Among 114 patients with HIT who received bivalirudin during
dialysis, no amputations were reported, 7 had new thromboembolic
events, and 32 died.57,126 For the 1 patient who received
rivaroxaban, no thromboembolic or bleeding events were
reported.127
Among patients without HIT receiving either citrate or heparin, the
risk of mortality was similar between treatment arms (RR, 0.97; 95%
CI, 0.84-1.13).131 The risk of bleeding was lower among patients
receiving regional citrate (RR, 0.3; 95% CI, 0.19-0.49). The risk of
development of HIT was lower among the patients receiving
regional citrate (RR, 0.41; 95% CI, 0.19-0.87). Among 3 patients
who received a second course of heparin more than 100 days after
an episode of acute HIT, none developed recurrent HIT.
Harms and burden. Patients may experience some harms
(eg, mortality and bleeding) from treatment with argatroban,
danaparoid, or bivalirudin, but this is uncertain. Among 97 patients
with HIT who received argatroban, 18 deaths were reported;
however, none were the result of thrombosis.111-120 One patient
with peripheral vascular disease underwent amputation, and 3
patients developed thrombotic events. Major bleeding occurred in 3
of 50 treatment courses in 1 study and in 2 of 30 patients in another
study. One patient required co-intervention with aspirin. Among
patients without HIT receiving danaparoid during hemodialysis, 2 of
25 developed nonfatal thromboembolic events, none required
amputation, 1 had minor bleeding, and 2 reported nonfatal adverse
events.70,121,122 Among 9 patients with HIT who received
fondaparinux during hemodialysis, 3 developed thromboses that
were managed by increasing the dose.123-125 Among 114 patients
with HIT who received bivalirudin during dialysis, 13 experienced
major bleeding events, 7 experienced new thromboembolic events,
and 32 died (HIT-related mortality was not disaggregated from all-
cause mortality).57,126
Other EtD criteria and considerations. Compared with
fondaparinux and rivaroxaban, argatroban, danaparoid, and bivalirudin
are less dependent on the kidneys for clearance. Citrate may have
similar efficacy and superior safety (reduced bleeding and reduced
HIT) compared with heparin in patients without a history of HIT. Citrate
is acceptable to clinicians and inexpensive compared with other non-
heparin anticoagulants (eg, argatroban, danaparoid, fondaparinux,
bivalirudin, and rivaroxaban) and therefore probably increases equity.
Conclusions and research needs for this recommendation.
The guideline panel suggests regional citrate rather than heparin or
other non-heparin anticoagulants on the basis of very low certainty
in the evidence. Citrate has similar efficacy and superior safety
(reduced bleeding and reduced HIT) compared with heparin in
patients without a history of HIT. It is familiar to clinicians and is
inexpensive compared with other non-heparin anticoagulants (eg,
argatroban, danaparoid, fondaparinux, bivalirudin, and rivaroxaban). No
research questions related to this recommendation were identified.
VTE and prophylaxis in patients with remote HIT
Question: Should a non-heparin anticoagulant (eg, apixaban,
dabigatran, danaparoid, edoxaban, fondaparinux, rivaroxaban, or a
VKA) or heparin be administered to patients with remote HIT who
require VTE treatment or prophylaxis?
Recommendation 7.1
In patients with remote HIT who require VTE treatment or
prophylaxis, the ASH guideline panel recommends admin-
istration of a non-heparin anticoagulant (eg, apixaban,
dabigatran, danaparoid, edoxaban, fondaparinux, rivarox-
aban, or a VKA) rather than UFH or LMWH (strong recom-
mendation, very low certainty in the evidence about effects
Å◯◯◯). Remarks: For recommendations on the choice of
non-heparin anticoagulant for VTE prophylaxis, please refer
to American Society of Hematology Guidelines on Pre-
vention of Venous Thromboembolism in Surgical Hospital-
ized Patients (manuscript in preparation) and Prophylaxis
for Hospitalized and Nonhospitalized Medical Patients
(Schünemann HJ et al, Blood Advances, in press). For rec-
ommendations on the choice of agent for VTE treatment,
please refer to American Society of Hematology Guidelines
on Treatment of Acute VTE (manuscript in preparation).
Summary of the evidence. We did not identify any RCTs
comparing heparin to non-heparin anticoagulants for treatment of
patients with remote HIT who require VTE prophylaxis or treatment.
We identified 1 study that reported on development of thrombosis
and likelihood of recurrence of thrombocytopenia among patients
re-exposed to heparin.39 The study reported on the outcome of
27 NOVEMBER 2018 x VOLUME 2, NUMBER 22 ASH 2018 VTE GUIDELINES: HIT 3385
recurrent HIT. The EtD framework is shown online at https://dbep.
gradepro.org/profile/7B9F1760-2AC7-D97B-BAC8-
680F1B04A2EA.
Benefits. Similar benefits may be experienced by patients
with remote HIT who receive non-heparin anticoagulants or heparin
for the prevention or treatment of VTE; however, this is uncertain.
Three patients with serologically confirmed HIT received a second
course of heparin more than 100 days after an episode of acute
HIT.39 None developed recurrent HIT.
Harms and burden. The incidence of recurrent HIT in
patients with remote HIT treated with a course of heparin or LMWH
for VTE prophylaxis or treatment is not known. However, cases
highlighting the harms of recurrent HIT have been reported. The panel
agreed that HIT recurrence would be a serious consequence. Apart
from the prospect of recurrent HIT, adverse events associated with
heparin and non-heparin anticoagulants would be expected to be
similar for patients without HIT and with remote HIT.
Other EtD criteria and considerations. The panel placed
a high value on avoiding recurrent HIT and related serious
consequences, therefore favoring treatment with non-heparin
anticoagulants even though heparin is less expensive than non-
heparin anticoagulants. In addition, there are several non-heparin
anticoagulants available for VTE prophylaxis and treatment with
comparable benefits and harms in patients without a history of HIT.
Stakeholders would not find the treatment of patients with remote
HIT with heparin instead of non-heparin anticoagulants acceptable,
even though it would be feasible.
Conclusions and research needs for this recommendation.
The guideline panel recommends administration of a non-heparin
anticoagulant (eg, apixaban, dabigatran, danaparoid, edoxaban,
fondaparinux, rivaroxaban, or a VKA) rather than UFH or LMWH on
the basis of very low certainty in the evidence about effects. Apart
from the recommendation to avoid heparin anticoagulants, these
patients should be treated similarly to those without a history of HIT.
For recommendations on choice of non-heparin anticoagulant for
VTE prophylaxis, please refer to American Society of Hematology
Guidelines on Prevention of Venous Thromboembolism in Surgical
Hospitalized Patients and American Society of Hematology
Guidelines on Prevention of Venous Thromboembolism in Medical
Hospitalized Patients. For recommendations on choice of agent for
VTE treatment, please refer to American Society of Hematology
Guidelines on Treatment of Acute VTE. No research priorities
related to this recommendation were identified.
Emergency identification
Question: Should patients with a history of HIT carry or wear an
emergency identifier (eg, an emergency pendant or bracelet)?
Recommendation 8.1.a
In patients with a history of HIT in the last 3 months, the ASH
guideline panel suggests carrying or wearing an emergency
identifier (eg, an emergency pendant or bracelet) (conditional
recommendation, very low certainty in the evidence about ef-
fects Å◯◯◯). Remark: The emergency identifier should in-
clude the drug (heparin), the reaction to the drug (HIT), and the
date HIT was diagnosed.
Recommendation 8.1.b
In patients with a history of HIT more than 3 months ago, the
ASH panel suggests against carrying or wearing an emergency
identifier (conditional recommendation, very low certainty in the
evidence about effects Å◯◯◯).
Summary of the evidence. No RCTs were identified that
compared carrying vs not carrying an emergency identifier for
patients with a history of HIT. We identified 1 study that reported on
development of thrombosis and the likelihood of recurrence of
thrombocytopenia among patients re-exposed to heparin.39 One
study reported on current practices among children with hemophilia
who wore or did not wear an emergency identifier.132 The EtD
framework is shown online at https://dbep.gradepro.org/profile/
4136F0E9-871F-A458-A526-FE3BF6DEF8E8.
Benefits. The risk of HIT recurrence or exacerbation with
heparin re-exposure is greatest in the first 3 months after
diagnosis of acute HIT. Therefore, for patients with HIT diagnosed
less than 3 months ago, there may be large potential benefits to
wearing an emergency identifier, including a decreased risk of
recurrent HIT and a reduction in patient anxiety about the risk of
recurrent HIT.
There may be small benefit for patients with a history of HIT
diagnosed more than 3 months ago, but this is uncertain.
Among patients with remote HIT, 3 patients with serologically
confirmed HIT received a second course of heparin more than
100 days after the initial episode of HIT, and none developed
recurrent HIT.39
Harms and burden. Among patients diagnosed with HIT
less than 3 months ago, there may be a small risk of inappropriate
avoidance of heparin as a result of wearing an emergency
identifier, but this is uncertain. For patients diagnosed with HIT
more than 3 months ago, there are situations where heparin re-
exposure may be appropriate (eg, cardiac surgery), and avoidance
of heparin could result in inferior treatment. Indirect evidence from
patients without HIT (with hemophilia) suggests that 3% to 6%
experience adverse events from wearing a medical bracelet
(rashes and bruising).132
Other EtD criteria and considerations. There is possibly
important uncertainty or variability in how much patients value the main
outcomes. The panel placed greater weight on avoidance of recurrent
HIT through use of an emergency identifier than on the potential for
inappropriate avoidance of heparin in the first 3 months, when the risk
of HIT recurrence with heparin re-exposure is relatively high. The panel
placed greater weight on the potential harms of inappropriate
avoidance of heparin than on the potential risk of recurrent HIT after
3 months, when the risk of HIT recurrence with heparin re-exposure is
relatively low. The costs of an emergency identifier are negligible.
Wearing an emergency identifier may not be acceptable to some
patients because of experienced or anticipated stigma. However, for
some patients, wearing an emergency identifier may decrease anxiety.
Emergency identifiers are feasible and acceptable to clinicians.
Conclusions and research needs for this recommendation.
The guideline panel suggests carrying or wearing an emergency
identifier (eg, an emergency pendant or bracelet) for patients with a
3386 CUKER et al 27 NOVEMBER 2018 x VOLUME 2, NUMBER 22
history of HIT in the last 3 months. The emergency identifier
should include the drug (heparin), the reaction to the drug
(HIT), and the date HIT was diagnosed. The guideline panel
suggests against carrying or wearing an emergency identifier
for patients with a history of HIT diagnosed more than 3 months
ago. No research priorities related to this recommendation
were identified.
What are others saying and what is new in
these ASH guidelines?
This guideline differs from previously published guidelines on
HIT in a number of respects. Two key differences are highlighted
here.
Although other recent guidelines have included individual
recommendations on diagnosing suspected HIT,52,133,134 our
guideline is the first to integrate multiple recommendations
regarding diagnosis and initial management of patients with
suspected HIT into an algorithm for clinicians (see recommenda-
tions 2.1 through 2.10 and Figure 1). The recommendations that
make up the algorithm are based on a novel modeling strategy that
incorporated not only the diagnostic accuracy of various tests for
HIT but also the impact of those tests on patient-important
outcomes, such as thrombosis, amputation, major bleeding, and
mortality.
Other guidelines either do not recommend fondaparinux52 or
suggest a preference for conventional non-heparin anticoagulants
(eg, danaparoid or argatroban) over fondaparinux133 for the
treatment of acute HIT. Those guidelines do not address the use
of DOACs in the management of acute HIT. In contrast, our
guideline suggests that danaparoid, argatroban, bivalirudin, fonda-
parinux, and DOACs are all potentially suitable for the treatment
of acute HIT and provides guidance on selecting anticoagulants
for individual patients (see recommendation 3.1. and accompa-
nying remarks).
Limitations of these guidelines
The limitations of these guidelines are inherent in the low or very
low certainty in the evidence we identified for many of the
questions. For most recommendations, there were few to no
comparative studies in patients with a confirmed diagnosis of
HIT. For some recommendations, studies of patients without HIT
were used as indirect evidence. For this reason, the certainty in
the evidence was often down-rated for indirectness. When
searching for evidence for the diagnosis of HIT and subsequent
management while awaiting a confirmed diagnosis, we also
found no studies assessing the impact of different diagnostic
strategies on outcomes important to patients such as mortality
and thrombotic events. Instead, we modeled the outcomes on
the basis of the numbers of true positives and false positives
and true negatives and false negatives. When modeling, we
assumed that the gold standard for confirmation of HIT was a
functional assay such as the SRA or heparin-induced platelet
activation assay. Although diagnostic test accuracy of the
functional assay is not 100%, this assumption was consistently
applied across models for all tests. Finally, nonfinancial conflicts
of interest, such as intellectual conflicts, were declared and
reviewed but did not result in recusal during the decision
process.
Revision or adaptation of the guidelines
Plans for updating these guidelines
After these guidelines are published, ASH will maintain them through
surveillance for new evidence, ongoing review by experts, and
regular revisions.
Updating or adapting recommendations locally
Adaptation of these guidelines will be necessary in many circum-
stances. These adaptations should be based on the associated EtD
frameworks.135
Priorities for research
On the basis of gaps in evidence recognized during the guideline
development process, the panel identified a number of priorities for
future research. Specific suggestions are detailed with each
recommendation. Key research priorities with respect to diagnosis
include integration of emerging rapid immunoassays into diagnostic
algorithms, identification of barriers to adherence to and implementa-
tion analyses of evidence-based diagnostic algorithms, and develop-
ment of novel laboratory assays that overcome limitations of currently
available assays (ie, immunoassays with enhanced specificity and
functional assays with enhanced practicability). Key research priorities
with respect to management include direct comparisons of non-
heparin anticoagulants for treatment of acute HIT, obtaining more data
on the efficacy and safety of DOACs in this setting, elucidation of the
role of intravenous immunoglobulin in acute HIT, and development of
novel therapeutics that target pathways in the pathogenesis of HIT
proximal to coagulation that could be effective in reducing thrombosis
without increasing the risk of hemorrhage.
Acknowledgments
The authors thank Housne Ara, Vahid Ashoorion, Nina Martinez, and
StephanieRoss for supporting the systematic reviews; Itziar Etxeandia
and Yuan Zhang for other assistance; and Robby Nieuwlaat, Wojtek
Wiercioch, and Holger Schünemann for being coordinators of the
systematic review team. Holger Schünemann prepared a template of
these guidelines for all panels, which was critically reviewed by Adam
Cuker, Rob Kunkle, the ASHGuideline Oversight Subcommittee, the
Methods Group supporting the guidelines, and editors of Blood
Advances.
Authorship
Contribution: A.C., R.L.M., and N.S. wrote the manuscript; guideline
panel members A.C., G.M.A., B.H.C., D.B.C., A.G., Y.J.G., L.A.L.,
S.B.R., S.S., T.E.W., A.W., and N.S. critically reviewed the manu-
script and provided suggestions for improvement; members of the
knowledge synthesis team R.A.M., R.L.M., and N.S. contributed ev-
idence summaries to the guidelines; all authors approved of the
content; and A.C. was chair and N.S. was vice chair of the panel and
led the panel meeting.
Conflict-of-interest disclosure: All authors were members of the
guideline panel or members of the systematic review team or both.
They completed disclosure-of-interest forms, which were reviewed
by ASH and are available as supplements 2 and 3.
Correspondence: Adam Cuker, Penn Comprehensive Hemo-
philia and Thrombosis Program, Hospital of the University of Penn-
sylvania, 3400 Spruce St, Philadelphia, PA 19104; e-mail: adam.
cuker@uphs.upenn.edu.
27 NOVEMBER 2018 x VOLUME 2, NUMBER 22 ASH 2018 VTE GUIDELINES: HIT 3387
References
1. Schünemann HJ, Wiercioch W, Etxeandia I, et al. Guidelines 2.0: systematic development of a comprehensive checklist for a successful guideline
enterprise. CMAJ. 2014;186(3):E123-E142.
2. Institute of Medicine. Clinical Practice Guidelines We Can Trust. Washington, DC: The National Academies Press; 2011. https://doi.org/10.17226/
13058.
3. Qaseem A, Forland F, Macbeth F, Ollenschläger G, Phillips S, van der Wees P; Board of Trustees of the Guidelines International Network. Guidelines
International Network: toward international standards for clinical practice guidelines. Ann Intern Med. 2012;156(7):525-531.
4. Schünemann HJ, Al-Ansary LA, Forland F, et al; Board of Trustees of the Guidelines International Network. Guidelines International Network: principles
for disclosure of interests and management of conflicts in guidelines. Ann Intern Med. 2015;163(7):548-553.
5. Alonso-Coello P, Oxman AD, Moberg J, et al; GRADE Working Group. GRADE Evidence to Decision (EtD) frameworks: a systematic and transparent
approach to making well informed healthcare choices. 2: Clinical practice guidelines. BMJ. 2016;353:i2089.
6. Alonso-Coello P, Schünemann HJ, Moberg J, et al; GRADE Working Group. GRADE Evidence to Decision (EtD) frameworks: a systematic and
transparent approach to making well informed healthcare choices. 1: Introduction. BMJ. 2016;353:i2016.
7. Atkins D, Eccles M, Flottorp S, et al; GRADEWorking Group. Systems for grading the quality of evidence and the strength of recommendations I: critical
appraisal of existing approaches The GRADE Working Group. BMC Health Serv Res. 2004;4(1):38.
8. Guyatt G, Oxman AD, Akl EA, et al. GRADE guidelines: 1. Introduction-GRADE evidence profiles and summary of findings tables. J Clin Epidemiol. 2011;
64(4):383-394.
9. Guyatt GH, Oxman AD, Vist GE, et al; GRADE Working Group. GRADE: an emerging consensus on rating quality of evidence and strength of
recommendations. BMJ. 2008;336(7650):924-926.
10. Schünemann HJ, Best D, Vist G, Oxman AD; GRADE Working Group. Letters, numbers, symbols and words: how to communicate grades of evidence
and recommendations. CMAJ. 2003;169(7):677-680.
11. Schünemann HJ, Mustafa R, Brozek J, et al; GRADE Working Group. GRADE Guidelines: 16. GRADE evidence to decision frameworks for tests in
clinical practice and public health. J Clin Epidemiol. 2016;76:89-98.
12. Amiral J, Bridey F, Vissoc AM, et al. Platelet factor 4 complexed to heparin is the target for antibodies generated in heparin-induced thrombocytopenia.
Thromb Haemost. 1992;68(1):95-96.
13. Rice L. Heparin-induced thrombocytopenia: myths and misconceptions (that will cause trouble for you and your patient). Arch Intern Med. 2004;164(18):
1961-1964.
14. Martel N, Lee J, Wells PS. Risk for heparin-induced thrombocytopenia with unfractionated and low-molecular-weight heparin thromboprophylaxis: a meta-
analysis. Blood. 2005;106(8):2710-2715.
15. Smythe MA, Koerber JM, Mattson JC. The incidence of recognized heparin-induced thrombocytopenia in a large, tertiary care teaching hospital. Chest.
2007;131(6):1644-1649.
16. Warkentin TE, Sheppard JA, Horsewood P, Simpson PJ, Moore JC, Kelton JG. Impact of the patient population on the risk for heparin-induced
thrombocytopenia. Blood. 2000;96(5):1703-1708.
17. Warkentin TE, Kelton JG. A 14-year study of heparin-induced thrombocytopenia. Am J Med. 1996;101(5):502-507.
18. Nand S, Wong W, Yuen B, Yetter A, Schmulbach E, Gross Fisher S. Heparin-induced thrombocytopenia with thrombosis: incidence, analysis of risk
factors, and clinical outcomes in 108 consecutive patients treated at a single institution. Am J Hematol. 1997;56(1):12-16.
19. Greinacher A, Farner B, Kroll H, Kohlmann T, Warkentin TE, Eichler P. Clinical features of heparin-induced thrombocytopenia including risk factors for
thrombosis. A retrospective analysis of 408 patients. Thromb Haemost. 2005;94(1):132-135.
20. Greinacher A, Eichler P, Lubenow N, Kwasny H, Luz M. Heparin-induced thrombocytopenia with thromboembolic complications: meta-analysis of 2
prospective trials to assess the value of parenteral treatment with lepirudin and its therapeutic aPTT range. Blood. 2000;96(3):846-851.
21. Rauova L, Poncz M, McKenzie SE, et al. Ultralarge complexes of PF4 and heparin are central to the pathogenesis of heparin-induced thrombocytopenia.
Blood. 2005;105(1):131-138.
22. Warkentin TE, Hayward CP, Boshkov LK, et al. Sera from patients with heparin-induced thrombocytopenia generate platelet-derived microparticles with
procoagulant activity: an explanation for the thrombotic complications of heparin-induced thrombocytopenia. Blood. 1994;84(11):3691-3699.
23. Pouplard C, Iochmann S, Renard B, et al. Induction of monocyte tissue factor expression by antibodies to heparin-platelet factor 4 complexes developed
in heparin-induced thrombocytopenia. Blood. 2001;97(10):3300-3302.
24. Kasthuri RS, Glover SL, Jonas W, et al. PF4/heparin-antibody complex induces monocyte tissue factor expression and release of tissue factor positive
microparticles by activation of FcgRI. Blood. 2012;119(22):5285-5293.
25. Blank M, Shoenfeld Y, Tavor S, et al. Anti-platelet factor 4/heparin antibodies from patients with heparin-induced thrombocytopenia provoke direct
activation of microvascular endothelial cells. Int Immunol. 2002;14(2):121-129.
26. Xiao Z, Visentin GP, Dayananda KM, Neelamegham S. Immune complexes formed following the binding of anti-platelet factor 4 (CXCL4) antibodies to
CXCL4 stimulate human neutrophil activation and cell adhesion. Blood. 2008;112(4):1091-1100.
27. Wallis DE, Workman DL, Lewis BE, Steen L, Pifarre R, Moran JF. Failure of early heparin cessation as treatment for heparin-induced thrombocytopenia.
Am J Med. 1999;106(6):629-635.
3388 CUKER et al 27 NOVEMBER 2018 x VOLUME 2, NUMBER 22
28. Lewis BE, Wallis DE, Berkowitz SD, et al; ARG-911 Study Investigators. Argatroban anticoagulant therapy in patients with heparin-induced
thrombocytopenia. Circulation. 2001;103(14):1838-1843.
29. Chong BH, Gallus AS, Cade JF, et al; Australian HIT Study Group. Prospective randomised open-label comparison of danaparoid with dextran 70 in the
treatment of heparin-induced thrombocytopaenia with thrombosis: a clinical outcome study. Thromb Haemost. 2001;86(5):1170-1175.
30. Lubenow N, Eichler P, Lietz T, Greinacher A; Hit Investigators Group. Lepirudin in patients with heparin-induced thrombocytopenia - results of the third
prospective study (HAT-3) and a combined analysis of HAT-1, HAT-2, and HAT-3. J Thromb Haemost. 2005;3(11):2428-2436.
31. Kuter DJ, Konkle BA, Hamza TH, et al. Clinical outcomes in a cohort of patients with heparin-induced thrombocytopenia. Am J Hematol. 2017;92(8):
730-738.
32. Warkentin TE, Levine MN, Hirsh J, et al. Heparin-induced thrombocytopenia in patients treated with low-molecular-weight heparin or unfractionated
heparin. N Engl J Med. 1995;332(20):1330-1335.
33. Warkentin TE. Fondaparinux for treatment of heparin-induced thrombocytopenia: too good to be true? J Am Coll Cardiol. 2017;70(21):2649-2651.
34. Warkentin TE, Davidson BL, Büller HR, et al. Prevalence and risk of preexisting heparin-induced thrombocytopenia antibodies in patients with acute VTE.
Chest. 2011;140(2):366-373.
35. Warkentin TE, Sheppard JA, Sigouin CS, Kohlmann T, Eichler P, Greinacher A. Gender imbalance and risk factor interactions in heparin-induced
thrombocytopenia. Blood. 2006;108(9):2937-2941.
36. Lubenow N, Hinz P, Thomaschewski S, et al. The severity of trauma determines the immune response to PF4/heparin and the frequency of heparin-
induced thrombocytopenia. Blood. 2010;115(9):1797-1803.
37. Sanson BJ, Lensing AW, Prins MH, et al. Safety of low-molecular-weight heparin in pregnancy: a systematic review. Thromb Haemost. 1999;81(5):668-
672.
38. Obeng EA, Harney KM, Moniz T, Arnold A, Neufeld EJ, Trenor CC. Pediatric heparin-induced thrombocytopenia: prevalence, thrombotic risk, and
application of the 4Ts scoring system. J Pediatr. 2015;166(1):144-150.
39. Warkentin TE, Kelton JG. Temporal aspects of heparin-induced thrombocytopenia. N Engl J Med. 2001;344(17):1286-1292.
40. Pon TK, Mahajan A, Rosenberg A, et al. Platelet response to direct thrombin inhibitor or fondaparinux treatment in patients with suspected heparin-
induced thrombocytopenia. J Thromb Thrombolysis. 2018;45(4):536-542.
41. Cuker A. Management of the multiple phases of heparin-induced thrombocytopenia. Thromb Haemost. 2016;116(5):835-842.
42. Cuker A, Gimotty PA, Crowther MA, Warkentin TE. Predictive value of the 4Ts scoring system for heparin-induced thrombocytopenia: a systematic
review and meta-analysis. Blood. 2012;120(20):4160-4167.
43. Lo B, Baldwin W, Bellini L, et al. Conflict of Interest in Medical Research, Education, and Practice. Washington, DC: National Academies Press; 2009.
44. Akl EA, El-Hachem P, Abou-Haidar H, Neumann I, Schünemann HJ, Guyatt GH. Considering intellectual, in addition to financial, conflicts of interest
proved important in a clinical practice guideline: a descriptive study. J Clin Epidemiol. 2014;67(11):1222-1228.
45. Guyatt G, Akl EA, Hirsh J, et al. The vexing problem of guidelines and conflict of interest: a potential solution. Ann Intern Med. 2010;152(11):738-741.
46. Schünemann HJ, Osborne M, Moss J, et al; ATS Ethics and Conflict of Interest Committee and the Documents Development and Implementation
Committee. An official American Thoracic Society Policy statement: managing conflict of interest in professional societies. Am J Respir Crit Care Med.
2009;180(6):564-580.
47. Brożek J, Nowak A, Kunstman P, Schünemann HJ. GRADEpro Guideline Development Tool (GDT). Available at: www.guidelinedevelopment.org.
Accessed 13 September 2018.
48. Guyatt GH, Oxman AD, Kunz R, et al. GRADE guidelines: 2. Framing the question and deciding on important outcomes. J Clin Epidemiol. 2011;64(4):
395-400.
49. Lubenow N, Kempf R, Eichner A, Eichler P, Carlsson LE, Greinacher A. Heparin-induced thrombocytopenia: temporal pattern of thrombocytopenia in
relation to initial use or reexposure to heparin. Chest. 2002;122(1):37-42.
50. Nagler M, Bachmann LM, ten Cate H, ten Cate-Hoek A. Diagnostic value of immunoassays for heparin-induced thrombocytopenia: a systematic review
and meta-analysis. Blood. 2016:127(5):546-557.
51. Sun L, Gimotty PA, Lakshmanan S, Cuker A. Diagnostic accuracy of rapid immunoassays for heparin-induced thrombocytopenia. A systematic review
and meta-analysis. Thromb Haemost. 2016;115(5):1044-1055.
52. Linkins LA, Dans AL, Moores LK, et al. Treatment and prevention of heparin-induced thrombocytopenia: antithrombotic therapy and prevention of
thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines. Chest. Journal. 2012;141(2 suppl):e495S-
e530S. doi:10.1378/chest.11-2303.
53. Lewis BE, Wallis DE, Leya F, Hursting MJ, Kelton JG; Argatroban-915 Investigators. Argatroban anticoagulation in patients with heparin-induced
thrombocytopenia. Arch Intern Med. 2003;163(15):1849-1856.
54. Kang M, Alahmadi M, Sawh S, Kovacs MJ, Lazo-Langner A. Fondaparinux versus argatroban and danaparoid for the treatment of suspected or confirmed
heparin-induced thrombocytopenia: A propensity score analysis [abstract]. Blood. 2012;120(21). Abstract 2262.
55. Al-Rossaies A, Alkharfy KM, Al-Ayoubi F, Al-Momen A. Heparin-induced thrombocytopenia: comparison between response to fondaparinux and lepirudin.
Int J Clin Pharm. 2011;33(6):997-1001.
56. Magnani HN, Gallus A. Heparin-induced thrombocytopenia (HIT). A report of 1,478 clinical outcomes of patients treated with danaparoid (Orgaran) from
1982 to mid-2004. Thromb Haemost. 2006;95(6):967-981.
27 NOVEMBER 2018 x VOLUME 2, NUMBER 22 ASH 2018 VTE GUIDELINES: HIT 3389
57. Joseph L, Casanegra AI, Dhariwal M, et al. Bivalirudin for the treatment of patients with confirmed or suspected heparin-induced thrombocytopenia.
J Thromb Haemost. 2014;12(7):1044-1053.
58. Warkentin TE, Pai M, Linkins LA. Direct oral anticoagulants for treatment of HIT: update of Hamilton experience and literature review. Blood. 2017;
130(9):1104-1113.
59. Schindewolf M, Scheuermann J, Kroll H, et al. Application, tolerance and safety of fondaparinux therapy in a German hospital: a prospective single-centre
experience. Thromb Res. 2012;129(1):17-21.
60. Greinacher A, Janssens U, Berg G, et al. Lepirudin (recombinant hirudin) for parenteral anticoagulation in patients with heparin-induced
thrombocytopenia. Heparin-Associated Thrombocytopenia Study (HAT) investigators. Circulation. 1999;100(6):587-593.
61. Farner B, Eichler P, Kroll H, Greinacher A. A comparison of danaparoid and lepirudin in heparin-induced thrombocytopenia. Thromb Haemost. 2001;
85(6):950-957.
62. Palatianos GM, Foroulis CN, Vassili MI, et al. Preoperative detection and management of immune heparin-induced thrombocytopenia in patients
undergoing heart surgery with iloprost. J Thorac Cardiovasc Surg. 2004;127(2):548-554.
63. Palatianos G, Michalis A, Alivizatos P, et al. Perioperative use of iloprost in cardiac surgery patients diagnosed with heparin-induced thrombocytopenia-
reactive antibodies or with true HIT (HIT-reactive antibodies plus thrombocytopenia): an 11-year experience. Am J Hematol. 2015;90(7):608-617.
64. Jung M, McCarthy JJ, Baker KR, Rice L. Safety of IVC filters with heparin-induced thrombocytopenia [abstract]. Blood. 2011;118(21). Abstract 2225.
65. Hong AP, Cook DJ, Sigouin CS, Warkentin TE. Central venous catheters and upper-extremity deep-vein thrombosis complicating immune heparin-
induced thrombocytopenia. Blood. 2003;101(8):3049-3051.
66. Mismetti P, Laporte S, Pellerin O, et al; PREPIC2 Study Group. Effect of a retrievable inferior vena cava filter plus anticoagulation vs anticoagulation alone
on risk of recurrent pulmonary embolism: a randomized clinical trial. JAMA. 2015;313(16):1627-1635.
67. Decousus H, Leizorovicz A, Parent F, et al. A clinical trial of vena caval filters in the prevention of pulmonary embolism in patients with proximal deep-vein
thrombosis. Prévention du Risque d’Embolie Pulmonaire par Interruption Cave Study Group. N Engl J Med. 1998;338(7):409-415.
68. Warkentin TE, Elavathil LJ, Hayward CP, Johnston MA, Russett JI, Kelton JG. The pathogenesis of venous limb gangrene associated with heparin-induced
thrombocytopenia. Ann Intern Med. 1997;127(9):804-812.
69. Srinivasan AF, Rice L, Bartholomew JR, et al. Warfarin-induced skin necrosis and venous limb gangrene in the setting of heparin-induced
thrombocytopenia. Arch Intern Med. 2004;164(1):66-70.
70. Lindhoff-Last E, Betz C, Bauersachs R. Use of a low-molecular-weight heparinoid (danaparoid sodium) for continuous renal replacement therapy in
intensive care patients. Clin Appl Thromb Hemost. 2001;7(4):300-304.
71. Goel R, Ness PM, Takemoto CM, Krishnamurti L, King KE, Tobian AA. Platelet transfusions in platelet consumptive disorders are associated with arterial
thrombosis and in-hospital mortality. Blood. 2015;125(9):1470-1476.
72. Refaai MA, Chuang C, Menegus M, Blumberg N, Francis CW. Outcomes after platelet transfusion in patients with heparin-induced thrombocytopenia.
J Thromb Haemost. 2010;8(6):1419-1421.
73. Hopkins CK, Goldfinger D. Platelet transfusions in heparin-induced thrombocytopenia: a report of four cases and review of the literature. Transfusion.
2008;48(10):2128-2132.
74. Senzel L, Coldren D. Negative heparin-induced thrombocytopenia test result after massive transfusion: believe it or not? Am J Clin Pathol. 2016;145(5):
717-719.
75. Tardy B, Tardy-Poncet B, Fournel P, Venet C, Jospe R, Dacosta A. Lower limb veins should be systematically explored in patients with isolated heparin-
induced thrombocytopenia. Thromb Haemost. 1999;82(3):1199-1200.
76. Elalamy I, Tardy-Poncet B, Mulot A, et al; GEHT HIT Study Group. Risk factors for unfavorable clinical outcome in patients with documented heparin-
induced thrombocytopenia. Thromb Res. 2009;124(5):554-559.
77. van Es N, Coppens M, Schulman S, Middeldorp S, Büller HR. Direct oral anticoagulants compared with vitamin K antagonists for acute venous
thromboembolism: evidence from phase 3 trials. Blood. 2014;124(12):1968-1975.
78. Koster A, Hansen R, Kuppe H, Hetzer R, Crystal GJ, Mertzlufft F. Recombinant hirudin as an alternative for anticoagulation during cardiopulmonary
bypass in patients with heparin-induced thrombocytopenia type II: a 1-year experience in 57 patients. J Cardiothorac Vasc Anesth. 2000;14(3):
243-248.
79. Koster A, Dyke CM, Aldea G, et al. Bivalirudin during cardiopulmonary bypass in patients with previous or acute heparin-induced thrombocytopenia and
heparin antibodies: results of the CHOOSE-ON trial. Ann Thorac Surg. 2007;83(2):572-577.
80. Dyke CM, Aldea G, Koster A, et al. Off-pump coronary artery bypass with bivalirudin for patients with heparin-induced thrombocytopenia or antiplatelet
factor four/heparin antibodies. Ann Thorac Surg. 2007;84(3):836-839.
81. Czosnowski QA, Finks SW, Rogers KC. Bivalirudin for patients with heparin-induced thrombocytopenia undergoing cardiovascular surgery. Ann
Pharmacother. 2008;42(9):1304-1309.
82. Smedira NG, Dyke CM, Koster A, et al. Anticoagulation with bivalirudin for off-pump coronary artery bypass grafting: the results of the EVOLUTION-OFF
study. J Thorac Cardiovasc Surg. 2006;131(3):686-692.
83. Riess FC, Poetzsch B, Madlener K, et al. Recombinant hirudin for cardiopulmonary bypass anticoagulation: a randomized, prospective, and heparin-
controlled pilot study. Thorac Cardiovasc Surg. 2007;55(4):233-238.
84. Dyke CM, Smedira NG, Koster A, et al. A comparison of bivalirudin to heparin with protamine reversal in patients undergoing cardiac surgery with
cardiopulmonary bypass: the EVOLUTION-ON study. J Thorac Cardiovasc Surg. 2006;131(3):533-539.
3390 CUKER et al 27 NOVEMBER 2018 x VOLUME 2, NUMBER 22
85. Merry AF, Raudkivi PJ, Middleton NG, et al. Bivalirudin versus heparin and protamine in off-pump coronary artery bypass surgery. Ann Thorac Surg. 2004;
77(3):925-931.
86. Carrier M, Robitaille D, Perrault LP, et al. Heparin versus danaparoid in off-pump coronary bypass grafting: results of a prospective randomized clinical
trial. J Thorac Cardiovasc Surg. 2003;125(2):325-329.
87. Magnani H, Beijering R, Ten Cate J, Chong B. Orgaran anticoagulation for cardiopulmonary bypass in patients with heparin-induced thrombocytopenia.
In: Pifarre R, ed. New Anticoagulants for the Cardiovascular Patient. Philadelphia, PA: Hanley and Belfus; 1997:487-500.
88. Jaben EA, Torloni AS, Pruthi RK, Winters JL. Use of plasma exchange in patients with heparin-induced thrombocytopenia: a report of two cases and a
review of the literature. J Clin Apher. 2011;26(4):219-224.
89. Huang R, Welsh KJ, Jacobi E, et al. Efficacy of therapeutic plasma exchange in heparin-induced thrombocytopenia patients prior to cardiac surgery with
heparin [abstract]. Transfusion. 2014;54. Abstract SP172.
90. Wadia Y, Cooper JR Jr, Bracey AW, Pinto K, Frazier OH. Intraoperative anticoagulation management during cardiac transplantation for a patient with
heparin-induced thrombocytopenia and a left ventricular assist device. Tex Heart Inst J. 2008;35(1):62-65.
91. Welsby IJ, Um J, Milano CA, Ortel TL, Arepally G. Plasmapheresis and heparin reexposure as a management strategy for cardiac surgical patients with
heparin-induced thrombocytopenia. Anesth Analg. 2010;110(1):30-35.
92. Aouifi A, Blanc P, Piriou V, et al. Cardiac surgery with cardiopulmonary bypass in patients with type II heparin-induced thrombocytopenia. Ann Thorac
Surg. 2001;71(2):678-683.
93. Makhoul RG, McCann RL, Austin EH, Greenberg CS, Lowe JE. Management of patients with heparin-associated thrombocytopenia and thrombosis
requiring cardiac surgery. Ann Thorac Surg. 1987;43(6):617-621.
94. Koster A, Meyer O, Fischer T, et al. One-year experience with the platelet glycoprotein IIb/IIIa antagonist tirofiban and heparin during cardiopulmonary
bypass in patients with heparin-induced thrombocytopenia type II. J Thorac Cardiovasc Surg. 2001;122(6):1254-1255.
95. Koster A, Kukucka M, Bach F, et al. Anticoagulation during cardiopulmonary bypass in patients with heparin-induced thrombocytopenia type II and renal
impairment using heparin and the platelet glycoprotein IIb-IIIa antagonist tirofiban. Anesthesiology. 2001;94(2):245-251.
96. Olinger GN, Hussey CV, Olive JA, Malik MI. Cardiopulmonary bypass for patients with previously documented heparin-induced platelet aggregation.
J Thorac Cardiovasc Surg. 1984;87(5):673-677.
97. Pötzsch B, Klövekorn WP, Madlener K. Use of heparin during cardiopulmonary bypass in patients with a history of heparin-induced thrombocytopenia.
N Engl J Med. 2000;343(7):515.
98. Selleng S, Haneya A, Hirt S, Selleng K, Schmid C, Greinacher A. Management of anticoagulation in patients with subacute heparin-induced
thrombocytopenia scheduled for heart transplantation. Blood. 2008;112(10):4024-4027.
99. Selleng S, Lubenow N, Wollert HG, Müllejans B, Greinacher A. Emergency cardiopulmonary bypass in a bilaterally nephrectomized patient with a history
of heparin-induced thrombocytopenia: successful reexposure to heparin. Ann Thorac Surg. 2001;71(3):1041-1042.
100. Warkentin TE, Sheppard JA. Serological investigation of patients with a previous history of heparin-induced thrombocytopenia who are reexposed to
heparin. Blood. 2014;123(16):2485-2493.
101. Davis Z, Anderson R, Short D, Garber D, Valgiusti A. Favorable outcome with bivalirudin anticoagulation during cardiopulmonary bypass. Ann Thorac
Surg. 2003;75(1):264-265.
102. Grocott HP, Root J, Berkowitz SD, deBruijn N, Landolfo K. Coagulation complicating cardiopulmonary bypass in a patient with heparin-induced
thrombocytopenia receiving the heparinoid, danaparoid sodium. J Cardiothorac Vasc Anesth. 1997;11(7):875-877.
103. Kappa JR, Cottrell ED, Berkowitz HD, et al. Carotid endarterectomy in patients with heparin-induced platelet activation: comparative efficacy of aspirin
and iloprost (ZK36374). J Vasc Surg. 1987;5(5):693-701.
104. Nuttall GA, OliverWC Jr, Santrach PJ, et al. Patients with a history of type II heparin-induced thrombocytopenia with thrombosis requiring cardiac surgery
with cardiopulmonary bypass: a prospective observational case series. Anesth Analg. 2003;96(2):344-350.
105. Warkentin TE, Sheppard JA, Chu FV, Kapoor A, Crowther MA, Gangji A. Plasma exchange to remove HIT antibodies: dissociation between enzyme-
immunoassay and platelet activation test reactivities. Blood. 2015;125(1):195-198.
106. Mahaffey KW, Lewis BE, Wildermann NM, et al; ATBAT Investigators. The anticoagulant therapy with bivalirudin to assist in the performance of percutaneous
coronary intervention in patients with heparin-induced thrombocytopenia (ATBAT) study: main results. J Invasive Cardiol. 2003;15(11):611-616.
107. Lewis BE, Matthai WH Jr, Cohen M, Moses JW, Hursting MJ, Leya F; ARG-216/310/311 Study Investigators. Argatroban anticoagulation during
percutaneous coronary intervention in patients with heparin-induced thrombocytopenia. Catheter Cardiovasc Interv. 2002;57(2):177-184.
108. Lee MS, Liao H, Yang T, et al. Comparison of bivalirudin versus heparin plus glycoprotein IIb/IIIa inhibitors in patients undergoing an invasive strategy: a
meta-analysis of randomized clinical trials. Int J Cardiol. 2011;152(3):369-374.
109. Jang IK, Lewis BE, Matthai WH Jr, Kleiman NS. Argatroban anticoagulation in conjunction with glycoprotein IIb/IIIa inhibition in patients undergoing
percutaneous coronary intervention: an open-label, nonrandomized pilot study. J Thromb Thrombolysis. 2004;18(1):31-37.
110. Hale LP, Smith K, Braden GA, Owen J. Orgaran during rotational atherectomy in the setting of heparin-induced thrombocytopenia. Cathet Cardiovasc
Diagn. 1998;45(3):318-322.
111. Link A, Girndt M, Selejan S, Mathes A, Böhm M, Rensing H. Argatroban for anticoagulation in continuous renal replacement therapy. Crit Care Med.
2009;37(1):105-110.
112. Reddy BV, Grossman EJ, Trevino SA, Hursting MJ, Murray PT. Argatroban anticoagulation in patients with heparin-induced thrombocytopenia requiring
renal replacement therapy. Ann Pharmacother. 2005;39(10):1601-1605.
27 NOVEMBER 2018 x VOLUME 2, NUMBER 22 ASH 2018 VTE GUIDELINES: HIT 3391
113. Matsuo T, Chikahira Y, Yamada T, Nakao K, Ueshima S, Matsuo O. Effect of synthetic thrombin inhibitor (MD805) as an alternative drug on heparin
induced thrombocytopenia during hemodialysis. Thromb Res. 1988;52(2):165-171.
114. Yamamoto S, Koide M, Matsuo M, et al. Heparin-induced thrombocytopenia in hemodialysis patients. Am J Kidney Dis. 1996;28(1):82-85.
115. Williamson DR, Boulanger I, Tardif M, Albert M, Grégoire G. Argatroban dosing in intensive care patients with acute renal failure and liver dysfunction.
Pharmacotherapy. 2004;24(3):409-414.
116. Matsuo T, Kario K, Chikahira Y, Nakao K, Yamada T. Treatment of heparin-induced thrombocytopenia by use of argatroban, a synthetic thrombin inhibitor.
Br J Haematol. 1992;82(3):627-629.
117. Koide M, Yamamoto S, Matsuo M, Suzuki S, Arima N, Matsuo T. Anticoagulation for heparin-induced thrombocytopenia with spontaneous platelet
aggregation in a patient requiring haemodialysis. Nephrol Dial Transplant. 1995;10(11):2137-2140.
118. Alatri A, Foramitti M, Paoletti O, Zimmermann A, Testa S. Treatment with argatroban in one haemodialysed patient with a heparin-induced
thrombocytopenia and thrombotic complications. Intern Emerg Med. 2010;5(4):359-360.
119. Athar U, Husain J, Hudson J, Lynch J, Gajra A. Prolonged half-life of argatroban in patients with renal dysfunction and antiphospholipid antibody syndrome
being treated for heparin-induced thrombocytopenia. Am J Hematol. 2008;83(3):245-246.
120. Barginear MF, Donahue L, Allen SL, et al. Heparin-induced thrombocytopenia complicating hemodialysis. Clin Appl Thromb Hemost. 2008;14(1):
105-107.
121. de Pont AC, Hofstra JJ, Pik DR, Meijers JC, Schultz MJ. Pharmacokinetics and pharmacodynamics of danaparoid during continuous venovenous
hemofiltration: a pilot study. Crit Care. 2007;11(5):R102.
122. Magnani HN. A review of 122 published outcomes of danaparoid anticoagulation for intermittent haemodialysis. Thromb Res. 2010;125(4):e171-e176.
123. Zerbi S, Manfrini V, Castellano A, Pezzotta M, Ruggiero P, Pedrini LA. Use of fondaparinux for extracorporeal circuit anticoagulation in patients with
heparin-induced thrombocytopenia type II (HIT II) on haemodiafiltration (HDF) [abstract]. Nephrol Dial Transplant. 2015;30(suppl_3):iii236. Abstract
FP493.
124. Haase M, Bellomo R, Rocktaeschel J, et al. Use of fondaparinux (ARIXTRA) in a dialysis patient with symptomatic heparin-induced thrombocytopaenia
type II. Nephrol Dial Transplant. 2005;20(2):444-446.
125. Brown P, Jay R, Fox A, Oliver M. Chronic fondaparinux use in a hemodialysis patient with heparin-induced thrombocytopenia type II and extracorporeal
circuit thrombosis-a case report and review of the literature. Hemodial Int. 2013;17(3):444-449.
126. Al-Ali FS, Elsayed M, Khalifa S, et al. Successful use of a bivalirudin treatment protocol to prevent extracorporeal thrombosis in ambulatory hemodialysis
patients with heparin-induced thrombocytopenia. Hemodial Int. 2016;20(2):204-207.
127. Ng HJ, Than H, Teo EC. First experiences with the use of rivaroxaban in the treatment of heparin-induced thrombocytopenia. Thromb Res. 2015;135(1):
205-207.
128. Murray PT, Reddy BV, Grossman EJ, et al. A prospective comparison of three argatroban treatment regimens during hemodialysis in end-stage renal
disease. Kidney Int. 2004;66(6):2446-2453.
129. Polkinghorne KR, McMahon LP, Becker GJ. Pharmacokinetic studies of dalteparin (Fragmin), enoxaparin (Clexane), and danaparoid sodium (Orgaran) in
stable chronic hemodialysis patients. Am J Kidney Dis. 2002;40(5):990-995.
130. Henny CP, ten Cate H, Surachno S, et al. The effectiveness of a low molecular weight heparinoid in chronic intermittent haemodialysis. ThrombHaemost.
1985;54(2):460-462.
131. Liu C, Mao Z, Kang H, Hu J, Zhou F. Regional citrate versus heparin anticoagulation for continuous renal replacement therapy in critically ill patients: a
meta-analysis with trial sequential analysis of randomized controlled trials. Crit Care. 2016;20(1):144.
132. Gorlin JB, Hooke MC, Leonard N. Use of emergency medical identification in the paediatric haemophilia population: a national study.Haemophilia. 2011;
17(2):215-222.
133. Watson H, Davidson S, Keeling D; Haemostasis and Thrombosis Task Force of the British Committee for Standards in Haematology. Guidelines on the
diagnosis and management of heparin-induced thrombocytopenia: second edition. Br J Haematol. 2012;159(5):528-540.
134. Smythe MA, Priziola J, Dobesh PP, Wirth D, Cuker A, Wittkowsky AK. Guidance for the practical management of the heparin anticoagulants in the
treatment of venous thromboembolism. J Thromb Thrombolysis. 2016;41(1):165-186.
135. Schünemann HJ, Wiercioch W, Brozek J, et al. GRADE Evidence to Decision (EtD) frameworks for adoption, adaptation, and de novo development of
trustworthy recommendations: GRADE-ADOLOPMENT. J Clin Epidemiol. 2017;81:101-110.
3392 CUKER et al 27 NOVEMBER 2018 x VOLUME 2, NUMBER 22