PT is a screening test that helps to assess the functionality of both the extrinsic and common pathways. The effectiveness and presence of factors I, II, V, VII, and X are assayed in this diagnostic test, as they are all found in the aforementioned pathways. The results of the PT test are used in conjunction with other diagnostic tests, as well as the clinical picture of the patient, to determine any hemostatic abnormalities that may be present.
In addition to being an integral part of the coagulation disorder assessment process, the PT is also used to determine therapeutic effectiveness of the oral anticoagulant, warfarin.
PT test results are reported as the number of seconds needed for a clot to form in the patient specimen using the laboratory's instrument/reagent system, and as the International Normalized Ratio (INR).