- Last Update On : 2013-03-03
The prothrombin time (PT or protime) is the actual time, measured in seconds, for an anticoagulated sample of plasma or whole blood to clot after it is added to a thromboplastin reagent. Thromboplastin is a mixture of tissue factor and calcium chloride. The PT assesses the coagulation factors of the extrinsic pathway (factors VII, X and V) and the factors in the common pathway (prothrombinase [a complex of activated factor X, activated factor V, and calcium which acts as the substrate for prothrombin], prothrombin, thrombin and fibrinogen). Physicians may request a PT to evaluate a patient:
- Investigate a history of a bleeding tendency prior to invasive surgical procedures
- Prior to intravascular cardiac surgery or other procedures that interfere with coagulation
- Determine the etiology of abnormal bleeding
- Assess liver function.
- Monitor warfarin therapy
The prothrombin time may be prolonged by deficiency of a singl