Thrombin time

The thrombin time (TT), also known as the thrombin clotting time (TCT), is a <a href="/facts/Blood_test/zevsf3rC">blood test</a> that measures the time it takes for a <a href="/facts/Clot/vH6FDIQG">clot</a> to form in the plasma of a blood sample containing <a href="/facts/Anticoagulant/cARpjm0G">anticoagulant</a>, after an excess of <a href="/facts/Thrombin/sU9x3MeH">thrombin</a> has been added. It is used to diagnose blood <a href="/facts/Coagulation/vnfEevM0">coagulation</a> disorders and to assess the effectiveness of fibrinolytic therapy. This test is repeated with pooled plasma from normal patients. The difference in time between the test and the 'normal' indicates an abnormality in the conversion of <a href="/facts/Fibrinogen/5dSBwGVo">fibrinogen</a> (a soluble protein) to fibrin, an insoluble protein.
The thrombin time compares the rate of clot formation to that of a sample of normal pooled plasma. Thrombin is added to the samples of plasma. If the time it takes for the plasma to clot is prolonged, a quantitative (fibrinogen deficiency) or qualitative (dysfunctional fibrinogen) defect is present. In blood samples suspected to contain <a href="/facts/Heparin/4lxSm2pB">heparin</a>, a substance derived from snake venom called <a href="/facts/Batroxobin/2MvRb3Ks">batroxobin</a> (formerly <a href="/facts/Reptilase/2MvRb3Ks">reptilase</a>) is used for comparison to thrombin time. Batroxobin has a similar action to thrombin but unlike thrombin it is not inhibited by heparin, so <a href="/facts/Reptilase_time/2jd1WyGp">reptilase time</a> and thrombin time can be used concurrently to distinguish anticoagulant effect from <a href="/facts/Hypofibrinogenemia/KJMI3tMR">hypofibrinogenemia</a> or <a href="/facts/Dysfibrinogenemia/TSn11hQR">dysfibrinogenemia</a>.
Normal values for thrombin time may be 12 to 14 seconds, but the test has significant reagent variability. If batroxobin is used, the time should be between 15 and 20 seconds. Thrombin time can be prolonged by heparin, fibrin degradation products, and fibrinogen deficiency or abnormality. Thrombin time is not affected by anti-Xa anticoagulants such as <a href="/facts/Rivaroxaban/lhH7t8rv">rivaroxaban</a> or <a href="/facts/Apixaban/lVvM6wAY">apixaban</a>, but is very sensitive to <a href="/facts/Direct_thrombin_inhibitors/y6ytmG70">direct thrombin inhibitors</a> including <a href="/facts/Dabigatran/qEzkkvr4">dabigatran</a>, <a href="/facts/Argatroban/0DoaMXAs">argatroban</a>, and <a href="/facts/Bivalirudin/YCyjsAUo">bivalirudin</a>.

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Thrombin time