The thrombin time (TT) measures the time it takes for clot formation in a plasma to which thrombin has been added. TT test is ordered as part of an investigation of a possible bleeding disorder or thrombotic episode. TT is prolonged by:
▪ Decreased fibrinogen levels (hypofibrinogenemia or afibrinogenemia).
▪ Abnormal function of fibrinogen (dysfibrinogenemia).
▪ Presence of direct thrombin inhibitors like Dabigatran, Bivalirudin and Argatroban.
▪ Presence of heparin.
▪ Presence of Aprotinin.
▪ Fibrinogen/fibrin degradation products and/or increased fibrinolysis e.g. due to thrombolytic therapy.
In newborns TT results above the normal range are observed.