is_about liver disorder blood plasma hematological measurement prothrombin time measurement true ProTime INR measurement Wikipedia:Prothrombin_time PT/INR measurement Laura Harris International normalized ratio of prothrombin time measurement PMID:22703881 Quantification of the clotting tendency of blood plasma following the addition of tissue factor. Prothrombin time requires the presence of factors I, II, V, VII, and X. It measures the extrinsic pathway of coagulation and can be used in conjunction with the activated partial thromboplastin time (aPTT) which measures the intrinsic pathway. It is used as a screening test and can be affected by vitamin K deficiency, liver disease, warfarin therapy or intestinal problems.