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Latest Edit: Hector 2014-03-24 (EDT)

See Also Lab Tests

The PTT, or Partial Thromboplastin Time test used to assess the intrinsic system and the common pathway of clot formation. It is also used to monitor heparin therapy. [1], [2]


  • PTT evaluates factors I (fibrinogen), II (prothrombin), V, VIII, IX, X, XI, XII involved in clotting.
  • Nearly all hemostatic abnormalities can be recognized when the PPT is combined with the prothrombin time.
  • On the other hand, heparin has been found to inactivate prothrombin (factor II) and to prevent the formation of thromboplastin.

Patient Preparation

  • No fasting required.
  • Factors which can cause increased levels
  • Drugs: antihistamines, ascorbic acid, chlorpromazine, heparin, and salicylates.
  • Factors which can cause decreased levels
  • None noted

Clinical Implications

High levels indicate:

  • Congenital clotting factor deficiencies (e.g. von Willebrand disease, hemophilia, hypofibrinogenemia)
  • Cirrhosis of the liver
  • Vitamin K deficiency
  • Diseeminated intravascular coagulation (DIC)
  • Heparin administration
  • Coumarin administration

Low levels indicate:

  • Early stages of DIC
  • Extensive cancer

Associated Tests

  • Bleeding time, Thrombin time, Prothrombin Time, Coagulating Factor Concentration


  1. Pagana Kathleen D, Pagana Timothy J (2006) Mosby's Manual of Diagnostic and Laboratory Tests, Mosby.
  2. Weatherby Dicken, Ferguson Scott (2002) Blood Chemistry and CBC Analysis: Clinical Laboratory Testing from a Functional Perspective, Bear Mountain.