Coagulation screening test

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Coagulation screening tests are a frequently conducted assay in dogs with suspected hemophilia or warfarin toxicity.

These are frequently conduced in cases of unexpected bleeding post-operatively or significant or unexpected blood loss associated with diarrhea or vomiting.

The assays essentially test in vitro the time required for fibrin clot formation. The prothrombin time is initiated by the addition of tissue factor and calcium to the test sample and is a measure of the extrinsic and common pathways. Patients deficient in one or more factors in this pathway demonstrate prolonged clotting time in the prothrombin time[1].

Clot formation in the activated partial thromboplastin time is initiated by a reagent containing phospholipid and negatively charged contact particles followed by the addition of calcium to the reaction mixture. This test is sensitive to factor deficiencies in the intrinsic and common pathways.

The activated clotting time is a simplified test that is influenced by platelet count, platelet dysfunction, hematocrit and plasma protease activity[2].


  1. Furie B & Furie BC (1992) Molecular and cellular biology of blood coagulation. N Engl J Med 326:800-806
  2. Jobes DR et al (1989) Limitations for ACT. Anesth Analg 69:142-144