Clot formation is detected optically or mechanically by a coagulation instrument. Thrombin time can be prolonged by heparin, fibrin degradation products, and fibrinogen deficiency or abnormality.Īfter separating the plasma from the whole blood by centrifugation, bovine thrombin is added to the sample of plasma. If batroxobin is used, the time should be between 15 and 20 seconds. Normal values for thrombin time are 12 to 14 seconds. Batroxobin has a similar action to thrombin but unlike thrombin it is not inhibited by heparin. In blood samples containing heparin, a substance derived from snake venom called batroxobin (formerly reptilase) is used instead of thrombin. If the time it takes for the plasma to clot is prolonged, a quantitative (fibrinogen deficiency) or qualitative (dysfunctional fibrinogen) defect is present. Thrombin is added to the samples of plasma. The thrombin time compares the rate of clot formation to that of a sample of normal pooled plasma. The difference in time between the test and the 'normal' indicates an abnormality in the conversion of fibrinogen (a soluble protein) to fibrin, an insoluble protein. This test is repeated with pooled plasma from normal patients. It is used to diagnose blood coagulation disorders and to assess the effectiveness of fibrinolytic therapy. The thrombin time ( TT), also known as the thrombin clotting time ( TCT), is a blood test that measures the time it takes for a clot to form in the plasma of a blood sample containing anticoagulant, after an excess of thrombin has been added.
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