what does inr measure
The prothrombin time (PT) â along with its derived measures of prothrombin ratio (PR) and international normalized ratio (INR) â are assays evaluating the extrinsic pathway of coagulation.This test is also called ProTime INR and PT/INR.They are used to determine the clotting tendency of blood, in the measure of warfarin dosage, liver damage, and vitamin K status. PT measures factors I (fibrinogen) , II (prothrombin) , V, VII, and X.aboratory measurement [edit]. The reference range for prothrombin time depends on the analytical method used, but is usually around 12â13 seconds (results should always be interpreted using the reference range from the laboratory that performed the test), and the INR in absence of anticoagulation therapy is 0.8-1.2.