Blood/Coagulation Tests

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  • Activated partial thromboplastin time: APTT - Intrinsic pathway
  • International Normalized Ratio: INR - extrinsic pathway
  • Thrombin (or prothrombin) time: TT / PTT - Common pathway


  • Abnormal APTT, INR; normal TT:
    • Combined Factor deficiencies
    • Warfarin therapy/Vitamin K deficiency
    • Liver disease (INR>APTT)
    • Lupus inhibitor (APTT>INR)
  • Abnormal APTT, INR, TT
    • Fibrinogen deficiency
    • Presence of fibrin degradation products/D-dimers (eg. DIC)
    • Drugs (heparin)

Notes