Detection of lupus anticoagulant--an Australian perspective

The detection of lupus anticoagulant is important in laboratory evaluation of patients with thrombotic tendencies. The aim of this workshop was to assess the effectiveness of Australian laboratories in detecting these antibodies and assess the tests used. Fourteen laboratories took part in the exercise, held as a Workshop of the National Meeting of Australian Medical Laboratory Scientists in 1990. Seven unknown plasmas were distributed for testing prior to the meeting. While 100% correctly identified 3 strong inhibitors and a moderate strength inhibitor, the detection rate for specific individual tests varied from 38-100%. The detection rate for 2 weak inhibitors varied from 0-50%. Of the most commonly performed tests the least sensitive was the dilute Russell's viper venom time and the most sensitive was the tissue thromboplastin inhibition test, however, the degree of sensitivity seemed dependent on the source of thromboplastin. In some laboratories the Kaolin clotting time, with variations, was more sensitive. All participants correctly identified a factor VIII inhibitor as not of the lupus type. The false positive detection rate was 0%. All but one of the participating laboratories used 2 or more phospholipid dependent tests for the analysis of lupus anticoagulant (LA) which is in keeping with current international guidelines.