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UW Health SMPH
American Family Children's Hospital

UW Hospital and Clinics Lab Test Directory

Test Name: Thrombin Time

Test Code(s): CTT / HCCTT

CPT Code(s): 85670

Test Description: Included In: May be included in a Lupus Anticoagulant Work-Up.

Methodology: Mechanical Clot Detection

Clinical Significance: The thrombin time measures the rate of fibrinogen to fibrin conversion in plasma in the presence of limited quantities of thrombin.

Prolongation of the thrombin time occurs when: the fibrinogen content is very low (less than 75 mg/dL), fibrin degradation products (FDP) are very high, heparin is present, or the fibrinogen is abnormal (i.e., dysfibrinogenemia).

Days Performed: Mon-Fri, dayshift - day varies. Specimens are accepted at any time. Testing required during off hours must be approved by a Coagulation physician. Call 263-5005 before collection.

Turnaround Time: Stat: 1 working day.
Routine: 4 - 7 working days.

Specimen Requirements

Specimen: Blood

Collection Instructions: Do NOT draw through a line containing heparin. The venipuncture MUST be atraumatic to avoid hemolysis and contamination with tissue factors and platelets. 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 on request form.

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

Collection Volume: Preferred: Full 3.5 mL tube
Pediatrics: Pediatric tube filled to fill mark

Sample Analyzed: Plasma

Volume Required: Preferred: 1 mL
Pediatrics: 1 mL

Specimen Processing: Centrifuge specimen to yield platelet poor plasma (platelet count should be less than 10 K/uL). Separate plasma and transfer to plastic tube or vial. Freeze plasma within 4 hours of collection at -20C or below.  

Specimen Transport: Transport whole blood specimen at room temperature to UWHC Core Laboratory (B4/220) within 4 hours of collection. See Specimen Processing for instructions if transport criteria are not met. Transport frozen plasma aliquot on dry ice to UWHC Core Laboratory (B4/220).

Unacceptable Criteria: Hemolyzed specimens, clotted specimens, partially filled tubes and whole blood specimens greater than 4 hours old when received by the laboratory are not acceptable.

Stability: Ambient: 4 hours on a spun tube
Refrigerated: Not acceptable
Frozen: 2 weeks at -20C; 6 months at -70C


Reference Interval:

Age 1 year and up: 15.0 - 20.0 seconds

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