INR

Prothrombin time

The prothrombin time (PT) – along with its derived measures of prothrombin ratio (PR) and international normalized ratio (INR) – is an assay for evaluating the extrinsic pathway and common pathway of coagulation. This blood test is also called protime INR and PT/INR. They are used to determine the clotting tendency of blood, in such things as the measure of 

• warfarin dosage
•  liver damage
• vitamin K status

PT measures the following coagulation factors:

•  I (fibrinogen)
• II (prothrombin)
•  V (proaccelerin)
• VII (proconvertin)
• X (Stuart–Prower factor). 

PTT  partial thromboplastin time (aPTT) measures the intrinsic pathway and common pathway of coagulation. [1]

INR

International normalized ratio