activated partial thromboplastin time (APTT)
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)