Advantage of Using Both Anionic and Zwitterionic Phospholipid Antigens for the Detection of Antiphospholipid Antibodies

To investigate the benefit of assaying for antiphospholipid antibodies (aPA) with different antigenic specificities, sera from 141 patients suspected of having aPA were tested by ELISA for IgG and IgM antibodies directed against the following phospholipids (PL) coated individually or together: cardiolipin, phosphatidylinositol, phosphatidylserine and phosphatidylethanolamine. Nonspecific background optical density (OD) was systematically subtracted from the test OD value. Positive reactions were defined as having an OD greater than the 97th percentile OD distribution obtained with sera from 100 healthy individuals. Although the majority of the 79 detected aPA (89% IgG and 77% IgM) were polyspecific, 11 reacted with a single PL and, moreover, belonged to only one isotype. Seven of these 11 patients presented recurrent fetal losses or thrombotic events. These results suggest that routine use of a mixture of both anionic and zwitterionic PL antigens to coat ELISA plates would better detect aPA involved in suggestive pathologies and enhance the ability to identify patients with these mono- or polyspecific antibodies directed or not against cardiolipin, the current standard.