EVALUATION OF SENSITIVITY AND SPECIFICITY OF A STANDARDIZED PROCEDUREUSING DIFFERENT REAGENTS FOR THE DETECTION OF LUPUS ANTICOAGULANTS

This study was designed to test the sensitivity and specificity of a c ombination of 3 phospholipid-dependent assays performed with various r eagents, for the detection of lupus anticoagulant(LA). Plasmas contain ing an LA (n = 56) or displaying various confounding pathologies [58 i ntrinsic pathway factor deficiencies, 9 factor VIII inhibitors, 28 pla smas from patients treated with an oral anticoagulant (OAC)] were sele cted. In a first step, the efficiency of each assay and reagent was as sessed using the Receiving Operating Characteristic (ROC) method. Opti mal cut-offs providing both sensitivity and specificity greater than o r equal to 80% were determined. The APTT assay and most of the phospho lipid neutralization assays failed to discriminate factor Vm inhibitor s from LA. In a second step, using the optimal cut-offs determined abo ve, the results of all the possible combinations of the 3 assays perfo rmed with 4 different reagents were analyzed. Thirteen combinations of reagents allowed greater than or equal to 80% of plasmas of each cate gory (LA, factor deficiency or OAC) to be correctly classified (3/3 po sitive test results in LA-containing plasmas and 0/3 positive results in LA-negative samples).