How should a prolonged activated partial thromboplastin time (aPTT) be interpreted?

Updated: Jul 02, 2021
  • Author: Muhammad Bader Hammami, MD; Chief Editor: Eric B Staros, MD  more...
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A prolonged aPTT result may indicate the following [1, 2] :

  • Congenital deficiencies of intrinsic system clotting factors such as factors VIII, IX, XI, and XII, including hemophilia A and hemophilia B (Christmas disease), two inherited bleeding disorders resulting from a deficiency in factors VIII and IX, respectively

  • Congenital deficiency of Fitzgerald factor (prekallikrein)

  • Von Willebrand disease, which is the most common inherited bleeding disorder, affecting platelet function owing to decreased von Willebrand factor activity

  • Liver cirrhosis (the liver makes most of the clotting factors, including those that are vitamin K-dependent ones); diseases of the liver may result in an inadequate quantity of clotting factors, prolonging the aPTT

  • Vitamin K deficiency: The synthesis of some clotting factors requires vitamin K, so vitamin K deficiency results in an inadequate quantity of intrinsic system and common pathways clotting factors, as a result the aPTT is prolonged

  • Disseminated intravascular coagulation (DIC): The clotting factors involved in the intrinsic pathway are consumed, prolonging the aPTT

  • Heparin therapy, which inhibits the intrinsic pathway at several points (eg, prothrombin II), prolonging the aPTT [4]

  • Coumarin therapy, which inhibits the function of factors I, IX and X, prolonging the aPTT

  • Nonspecific inhibitors, such as lupus anticoagulant and anticardiolipin antibodies, which bind to phospholipids on the surface of platelets

  • Specific circulating anticoagulants, inhibitor antibodies that specifically target certain coagulation factor, such as in individuals with hemophilia after many plasma transfusions, systemic lupus erythematosus, rheumatoid arthritis, tuberculosis, and chronic glomerulonephritis

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