Thrombin Time (TT) measures the ability of exogenous thrombin to proteolyse fibrinogen. Thus it is used to characterize fibrinogen function. It is prolonged in conditions like hypofibrinogenemia, dysfibrinogenemia, presence of fibrin degradation products, antibody inhibitors of thrombin and in conditions with high concentrations of monoclonal immunoglobulins which interfere with fibrin monomer polymerization like Myeloma & Macroglobulinemia.