Prothrombin Time

**Semantic type:** Laboratory Procedure

**Definition:** A measurement of the clotting time of plasma recalcified in the presence of excess tissue thromboplastin; it is a measure of the extrinsic pathway of coagulation. It is used to determine the clotting tendency of blood, in the measure of warfarin dosage, liver damage and vitamin K status. Factors measured are fibrinogen, prothrombin, and factors V, VII, and X.

**Synonyms:** - PT - PT - PT - Prothrombin Time Test