Comparison of four laboratory tests for lupus anticoagulant

The lupus anticoagulant (LA) phenomenon created world-wide interest recently. Various tests have been devised to identify LA in plasma, but none of these methods have been universally accepted. In this study 16 cases labelled LA positive by a prior kaolin clotting time (KCT) test were reassessed by four other methods, namely delta KCT (delta kaolin clotting time), APTT (activated partial thromboplastin time), PNP (platelet neutralization procedure), and DRVVT (dilute Russell viper venom time). Anti-cardiolipin antibodies (ACL) were also looked for. In our hands the delta KCT proved to be a simple, sensitive test, not influenced by oral anticoagulant therapy, and we recommend it as a screening test. Where the presence of LA is strongly suspected on clinical and other groups, more than one method may be necessary for the diagnosis.