Summary
This study was designed to test the sensitivity and specificity of a combination of
3 phospholipid-dependent assays performed with various reagents, for the detection
of lupus anticoagulant (LA). Plasmas containing an LA (n = 56) or displaying various
confounding pathologies [58 intrinsic pathway factor deficiencies, 9 factor VIII inhibitors,
28 plasmas from patients treated with an oral anticoagulant (OAC)] were selected.
In a first step, the efficiency of each assay and reagent was assessed using the Receiving
Operating Characteristic (ROC) method. Optimal cut-offs providing both sensitivity
and specificity ≥80% were determined. The APTT assay and most of the phospholipid
neutralization assays failed to discriminate factor VIII inhibitors from LA. In a
second step, using the optimal cut-offs determined above, the results of all the possible
combinations of the 3 assays performed with 4 different reagents were analyzed. Thirteen
combinations of reagents allowed ≥ 80% of plasmas of each category (LA, factor deficiency
or OAC) to be correctly classified (3/3 positive test results in LA-containing plasmas
and 0/3 positive results in LA-negative samples).
