A HEXAGONAL(II) PHASE PHOSPHOLIPID NEUTRALIZATION ASSAY FOR LUPUS ANTICOAGULANT IDENTIFICATION

Lupus anticoagulants (LAs) are immunoglobulins (IgG, IgM, or both) whi ch interfere with in vitro phospholipid (PL) dependent tests of coagul ation (e. g. APTT, dilute PT, dilute Russell Viper Venom Time). These antibodies may be identified in a wide variety of clinical settings. W ith the exception of heparinized patient samples, the presence of LAs is often the most common cause of an unexplained APTT in a routine cli nical laboratory. The diagnosis of LAs is difficult due to variable sc reening reagent sensitivity and intrinsic heterogeneity of LAs. Recent ly, Rauch and colleagues have shown human monoclonal hybridoma LAs wer e inhibited by hexagonal (II) phase PLs. In contrast, lamellar phase P Ls had no effect. We have evaluated a new assay system, Staclot LA(R), which utilizes a hexagonal (II) phase PL (egg phosphatidylethanolamin e [EPE]) as a confirmatory test for LAs. Plasma samples from the follo wing patient populations were studied: LA positive, heparinized, oral anticoagulated, hemophilia A and B, and specific factor inhibitors (fa ctors V, VIII, IX). Unlike previous studies, the LA positive patients were a mixed population including: autoimmune diseases, drug-induced, and post-infection. Our findings confirm the specificity of hexagonal (II) phase PL neutralization of LAs.