The [[prothrombin]] time (PT)—along with its derived measures of prothrombin ratio (PR) and [[international normalized ratio]] ([[INR]])—are assayed evaluating the extrinsic pathway of coagulation. This test is also called "ProTime INR" and "PT/INR". They are used to determine the [[clot]]ting tendency of [[blood]], in the measure of [[warfarin]] dosage, liver damage, and [[vitamin K]] status. PT measures factors I ([[Fibrinogen]]), II (Prothrombin), V ([[Proaccelerin]]), VII ([[Proconvertin]]), and X (Stuart–Prower Factor). It is used in conjunction with the [[activated partial thromboplastin time]] (aPTT) which measures the intrinsic pathway and common pathway.