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activated partial thromboplastin time (APTT)

see also:


  • the APTT test measures the overall activity of the intrinsic coagulation pathway.
  • performed by warming a thromboplastin reagent that contains phospholipid with an aliquot of the patient's plasma, and then recalcifying this mixture after a set incubation period.
  • length of time taken for the mixture to clot is called the APTT and the normal range is 26-39 secs, depending on the analyser and the brand of reagent used.

causes of a prolonged APTT

  • deficiency of one or more coagulation factors in the intrinsic coagulation pathway.
  • presence of a lupus type coagulation inhibitor - an in vitro phenomenon giving falsely prolonged results in some patients.
  • presence of heparin (but not LMW heparin)
aptt.txt · Last modified: 2009/09/01 14:45 (external edit)