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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.
[4] [10] The prolongation of the activated partial thromboplastin time should completely correct with a 1:1 mixing study with normal plasma if haemophilia C is present; in contrast, if a lupus anticoagulant is present as the cause of a prolonged aPTT, the aPTT will not correct with a 1:1 mixing study. [citation needed]
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]
Thrombotic thrombocytopenic purpura (TTP) is a blood disorder that results in blood clots forming in small blood vessels throughout the body. [2] This results in a low platelet count, low red blood cells due to their breakdown, and often kidney, heart, and brain dysfunction. [1]
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.
The prothrombin time can be prolonged as a result of deficiencies in vitamin K, warfarin therapy, malabsorption, or lack of intestinal colonization by bacteria (such as in newborns). In addition, poor factor VII synthesis (due to liver disease) or increased consumption (in disseminated intravascular coagulation) may prolong the PT. [citation ...
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 ...
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.