Prothrombin time

In hematology, the prothrombin time (PT) is a measurement of blood coagulation, specifically the clotting time of plasma recalcified in the presence of excess tissue thromboplastin, which measures the interactions of fibrinogen, prothrombin, Factor V, Factor VII and Factor X

While it is commonly used both for screening for abnormal coagulation and for monitoring anticoagulant therapy, it is subject to variations due to the reagents used. The International Normalized Ratio corrects for these variations, and is much more useful for managing anticoagulants.