International Normalized Ratio of Prothrombin Time

**Semantic type:** Laboratory Procedure

**Definition:** A measure of the extrinsic pathway of coagulation. The International Normalized Ratio of Prothrombin Time (INR) is the ratio of a patient prothrombin time to a normal (control) sample raised to the power of the International Sensitivity Index (ISI) with a range of 0.8 to 1.2 seconds.

**Synonyms:** - INR - INR - Prothrombin Intl. Normalized Ratio - Prothrombin Intl. Normalized Ratio