These tests are coagulation studies performed to assess the natural clotting ability of a sample of blood.
Abnormal results could be due to a number of reasons including, but, not limited to, deficiency in clotting factors, dysfunction of clotting factors, blood-thinning medications, medication side-effects, platelet deficiency, inherited bleeding or clotting disorders, liver disease, or advanced illness resulting in a medical emergency known as disseminated intravascular coagulation (DIC).
[5] There are several other methods, including testing for those on blood thinners, such as heparin or warfarin.
Activated partial thromboplastin time (aPTT) is used for heparin studies and the normal range is 20–36 seconds, depending upon which type of activator is used in the study.
[6] Prothrombin time (PT) is used for warfarin studies and the normal values differ for men and women.