Comparative assessment of phospholipid-binding antibodies indicates limited overlapping.

The implication of autoantibodies with anticoagulant and/or so-called antiphospholipid activities, under clinical circumstances with vascular obliteration, has led to the development of various types of tests allowing their detection. The most used tests involve investigation of the presence of an anticoagulant effect and of anticardiolipin IgG. It has also been proposed that the reactivity of patient samples toward other phospholipids or proteins be tested, but it remains difficult to appreciate which tests are redundant or complementary. Here we investigated whether the dissociation or association of anticoagulant and anticardiolipin correlated with specific ELISA reactivity to five other phospholipids: phosphatidylserine, phosphatidylinositol, phosphatidic acid, phosphatidylcholine, and phosphatidylethanolamine. The study was performed with 70 samples, evenly partitioned as positive for either anticardiolipin antibodies or anticoagulant effect, or both. Our data clearly confirm that cardiolipin reactivity is an individual entity, likely to be complementary to other assays. Neither anticardiolipin nor anticoagulant levels correlated with assays investigating antibody levels toward the five other phospholipids, although higher mean levels were noted when both lupus anticoagulant and anticardiolipin antibodies are present. Individual patterns were evidenced in all groups. These data support the interest of current and further studies exploring the clinical relevance of individual reactivities to phospholipids.