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Liver Function Tests
Liver Function Tests

International Normalised Ratio

February 15th, 2021


    • Normal Range

    • Prothrombin time - 11 - 15 sec
    • INR - 0.9 - 1.3
  • Significance

  • PT/INR is often elevated in patients with significant liver disease.
Liver disease produces coagulopathy through multiple mechanisms including coagulation factor deficiencies, vitamin K deficiency (due to fat malabsorption), dysfibrinogenaemia, thrombocytopaenia and reduced platelet function.
PT/INR does not directly correspond to the true coagulative status of patients with liver disease. Most often these patients are also coagulopathic due to elevated Von Willebrand factor and deficiencies in protein C, protein C, antithrombin and plasminogen.
  • Causes of Prolonged PT/INR

  • Isolated Prolonged PT/INR

  • Warfarin (low dose)
  • Mild vitamin K deficiency
  • Factor VII deficiency
  • Prolonged PT/INR and APTT

  • Artefactual - high haematocrit
  • Liver disease
  • Disseminated intravascular coagulation (DIC)
  • Common pathway deficiency - X, V, II, fibrinogen
  • Severe vitamin K deficiency
  • High dose heparin
  • Warfarin
  • Factor IIa inhibitors (dabigatran)
  • Factor Xa inhibitors (rivaroxaban, apixaban)
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