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UW Health SMPH
American Family Children's Hospital

UW Hospital and Clinics Lab Test Directory

Test Name: Platelet Function Screen

Test Code(s): PFS / HCPFS

CPT Code(s): 85576 x2

Test Description: Test Component:

Testing is performed using two cartridges: one with collagen/epinephrine (PFAEPI) and a second with collagen/ADP (PFAADP).

Methodology: Shear Flow Closure Time

Clinical Significance: Screen for platelet function. Especially recommended as part of a workup for von Willebrand disease.

Days Performed: Mon-Fri, 0800-1500 - day varies. Specimens will not be accepted prior to 0800 or after 1500. Testing required during off hours must be approved by a Coagulation physician. Call 263-5005 before collection.

Turnaround Time: Stat: 2 hours.
Routine: 4 hours.

Specimen Requirements

Specimen: Blood

Patient Preparation: Fasting specimen preferred. Patient ingestion of aspirin or aspirin-containing medications for 7 days and/or antihistamines, non-narcotic analgesics, or NSAIDs for 48 hours prior to specimen collection may cause abnormal results.

Collection Instructions: Indicate if von Willebrand disease is suspected. Do NOT draw through a line containing heparin. The venipuncture MUST be atraumatic to avoid hemolysis, contamination with tissue factors, or platelet activation. Tube must be allowed to fill completely.

Please indicate patient history and if patient is receiving anticoagulant (Coumadin/Heparin/Vitamin K antagonist), direct thrombin inhibitor or fibrinolytic agent therapy and duration.

Collection Container: Preferred: Light blue top (3.2% NaCitrate)

Collection Volume: Preferred: Two full 3.5 mL tubes
Pediatrics: 2 full pediatric tubes filled to mark

Sample Analyzed: Whole Blood

Volume Required: Preferred: 7 mL
Pediatrics: 3.6 mL

Specimen Processing: Do NOT freeze, refrigerate, or centrifuge. Do NOT open tube.

Specimen Transport: Hand deliver specimen to UWHC Core Laboratory (B4/220) ASAP. Do NOT send through pneumatic tube.

Unacceptable Criteria: Hemolyzed or clotted specimens are not acceptable. A partially filled tube is NOT acceptable.

Stability: Ambient: 4 hours unspun
Refrigerated: Not acceptable
Frozen: Not acceptable


Reference Interval:
 Age 1 years and up:  
 Collagen/Epinephrine  85-175 seconds
 Collagen/ADP  65-120 seconds


A reference interval has not been established for children less than 1 year of age.

Test Limitations:

Abnormal results on samples with hematocrit less than 25 mL/dL and/or platelet count less than 100 K/µL may be difficult to interpret.

Additional Information:

The PFA-100® system is an instrument in which the process of platelet adhesion and aggregation following a vascular injury is simulated in vitro. Use of cartridges coated with collagen and either epinephrine or ADP allows the differentiation of aspirin-induced platelet defect from congenital and acquired platelet dysfunction. Collagen/ADP is generally normal after ingesting aspirin. A normal Collagen/Epinephrine test with an abnormal Collagen/ADP test may be seen in mild von Willebrand disease. Results above the reference range should be interpreted in the context of the clinical history and other findings. Abnormal results on samples with hematocrits less than 25 mL/dL and/or platelet counts less than 100 K/µL may be difficult to interpret.

Platelet Func Collagen Epinephrine PFAEPI PFA Analyzer Test
Bleeding Time

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