A survey of aPTT reporting in Canadian Medical Laboratories - The need forincreased standardization

A survey of all licensed medical laboratories performing activated partial thromboplastin time (aPTT) testing in Canada was undertaken; the, response rate was 50.7%. Preanalytic phase of testing seemed generally satisfactory although 46% of laboratories were still using 3.8% or a 129-mmol/L concentr ation of citrate, and only 59% of institutions routinely performed testing to verify the platelet-poor status of the plasma used for aPTT testing. The re were also concerns relating to the speed and duration of centrifugation for specimen preparation. While more than 67% of institutions had establish ed an individual therapeutic range for aPTT testing, only 47% of laboratori es verified this range with heparinized samples. Approximately 67% of the i nstitutions that had verified the range had done this by spiking heparin co ncentrations into pooled plasma rather than using in vivo specimens from pa tients receiving heparin therapy. There seemed to be a need for increased e ducation about circumstances under which the therapeutic range should be re checked and current standards for screening for the lupus anticoagulant. Mo re than 71% of Canadian institutions surveyed ed used low-molecular weight heparin, which may obviate many of the issues surrounding aPTT testing. Ove rall performance as documented by survey results seemed similar to that rep orted for the United States and A Australasia.