see also:

• anticoagulants
• INR

• 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.

• 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)