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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.
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 ...
The basic purpose of these tests is to determine the cause of prolongation of Prothrombin Time (PT), Partial Thromboplastin Time, or sometimes of thrombin time (TT). Mixing studies take advantage of the fact that factor levels that are 50 percent of normal should give a normal Prothrombin time (PT) or Partial thromboplastin time (PTT) result. [2]
Thrombin time can be prolonged by heparin, fibrin degradation products, and fibrinogen deficiency or abnormality. Thrombin time is not affected by anti-Xa anticoagulants such as rivaroxaban or apixaban , but is very sensitive to direct thrombin inhibitors including dabigatran , argatroban , and bivalirudin .
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.
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.
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 ...
The aPTT-based APC resistance test involves a modified aPTT test performed in the presence and absence of activated protein C (APC). [1] [5] The ratio of these aPTT values is calculated and is called the APC sensitivity ratio (APCsr) or simply APC ratio (APCr). [1] [5] This ratio is inversely related to the degree of APC resistance. [7]