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Test Findings
 
 

Prolonged APTT

 
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Overview

  • Causes of Prolonged APTT

  • Isolated Prolonged APTT

  • Unfractionated heparin - therapeutic or contamination
  • Overcoagulation with low molecular weight heparin
  • Factor deficiency - VIII, IX, VI, XII
  • Factor inhibitors
  • Von Willebrand disease
  • Lupus anticoagulant (antiphospholipid antibody)
  • Prolonged APTT and PT/INR

  • Artefactual - high haematocrit
  • Liver disease
  • Disseminated intravascular coagulation (DIC)
  • Common pathway deficiency - X, V, II, fibrinogen
  • Severe vitamin K deficiency
  • Excess heparin (e.g. from heparin in the line)
  • Warfarin
  • Factor IIa inhibitors (dabigatran)
  • Factor Xa inhibitors (rivaroxaban, apixaban)
  • Approach

  • Determine whether the patient is on heparin or any other anticoagulants.
  • Check the patient’s haematocrit, which if elevated will falsely elevate PT/INR and APTT.
  • Look for evidence of chronic liver disease, either in the patient’s past medical history or current clinical state.
  • Assess the patient’s risk of DIC given their clinical state.
  • If unsure about the cause of prolonged APTT, mixing studies can be performed.
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    Snapshot: Initialising...