Prothrombin time measures the extrinsic coagulation pathway which consists of activated Factor VII (VIIa), Tissue factor and Proteins of the common pathway (Factors X, V, II & Fibrinogen). This assay is used to control long term oral anticoagulant therapy, evaluation of liver function & to evaluate coagulation disorders specially factors involved in the extrinsic pathway like Factors V, VII, X, Prothrombin & Fibrinogen.