Thrombin Time

Collect whole blood in 3.2% buffered sodium citrate (9:1 blood to sodium citrate). Venipuncture must be atraumatic.

• Centrifuge at 4,500 RPM (high) for 10 minutes. Plasma platelet count should be less than 10,000. Test within 2 hours of collection.
• If testing is to be delayed more than two hours after collection, immediately separate plasma into a clean, polystyrene tube, cap and store below -20°C up to two weeks or -70°C up to 6 months.
• In patients with hematocrit values greater than 55%, the citrate concentration must be adjusted so that a proper plasma/anticoagulant volume is maintained.

Venipuncture must be atraumatic. Reject hemolyzed, clotted, overfilled, or short draw (<90%) samples.

Thrombin is an enzyme in blood that acts on the clotting factor fibrinogen to form fibrin, helping blood to clot. The thrombin time assesses the activity of fibrinogen.

The thrombin time evaluates that part of the hemostatic process where soluble fibrinogen is changed into fibrin threads. It measures the time required for a fibrin clot to form following the addition of a standard amount of thrombin to plasma. It is affected by the level and/or function of fibrinogen and the presence of inhibitors (e.g., heparin, fibrinogen/fibrin degradation products, direct thrombin inhibitor). With the addition of thrombin to the test sample, the thrombin time bypasses the rest of the coagulation factors and focuses on the function of fibrinogen.