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The partial thromboplastin time (PTT), also known as the activated partial thromboplastin time (aPTT or APTT), is a blood test that characterizes coagulation of the blood. A historical name for this measure is the Kaolin-cephalin clotting time ( KCCT ), [ 1 ] reflecting kaolin and cephalin as materials historically used in the test.
Argatroban is used as an anticoagulant in individuals with thrombosis and heparin-induced thrombocytopenia. Often these individuals require long-term anticoagulation. If warfarin is chosen as the long-term anticoagulant, this poses particular challenges due to the falsely elevated prothrombin time and INR caused by argatroban.
The reference range for prothrombin time depends on the analytical method used, but is usually around 12–13 seconds (results should always be interpreted using the reference range from the laboratory that performed the test), and the INR in absence of anticoagulation therapy is 0.8–1.2.
Clotting time is a general term for the time required for a sample of blood to form a clot, or, in medical terms, coagulate.The term "clotting time" is often used when referring to tests such as the prothrombin time (PT), activated partial thromboplastin time (aPTT or PTT), activated clotting time (ACT), thrombin time (TT), or Reptilase time.
Fresh normal plasma has all the blood coagulation factors with normal levels. If the problem is a simple factor deficiency, mixing the patient plasma 1:1 with plasma that contains 100% of the normal factor level results in a level ≥50% in the mixture (say the patient has an activity of 0%; the average of 100% + 0% = 50%). [3]
Notably, when one examines the lab values in Vitamin K deficiency [see below] the prothrombin time is elevated, but the partial thromboplastin time is normal or only mildly prolonged. The deficiency leads to decreased activity in the intrinsic pathway (F-IX) factors, monitored by PTT, and the extrinsic pathway (F-VII) which PT monitors.
Nevertheless, falsely increased PT has been reported, likely by lupus anticoagulant interfering with the phospholipid component of the PT reagent, particularly when using recombinant tissue factor and purified phospholipids. [10] A mixing test is generally in the initial workup of a prolonged aPTT. In a mixing test, patient plasma is mixed with ...
Bleeding time may be affected by platelet function, certain vascular disorders and von Willebrand Disease—not by other coagulation factors such as haemophilia.Diseases that may cause prolonged bleeding time include thrombocytopenia, disseminated intravascular coagulation (DIC), Bernard-Soulier disease, and Glanzmann's thrombasthenia.