PREVALENCE AND CLINICAL-SIGNIFICANCE OF IGG ISOTYPE ANTI-BETA(2)-GLYCOPROTEIN-I ANTIBODIES IN ANTIPHOSPHOLIPID SYNDROME - A COMPARATIVE-STUDY WITH ANTICARDIOLIPIN ANTIBODIES

To investigate the prevalence, significance, and specificity of lgG is otype anti-p,Glycoprotein I antibodies (a-beta 2-GPI) in antiphospholi pid syndrome (APS), we developed an enzyme-linked immunosorbent assay (ELISA) for the detection of IgG-a-beta(2),-GPI and tested sera from 6 1 patients with autoimmune disorders (AID), 39 patients with APS and 2 2 patients with systemic lupus erythematosus without APS, 139 patients with various infectious diseases (hepatitis C virus infection, human immunodeficiency virus infection, Q fever, Mediterranean spotted fever , syphilis) and 97 healthy control subjects. Using irradiated plates c oated with human beta(2)-GPI, we showed that in the sera of patients w ith AID, optical densities from the coated wells were significantly hi gher than those from the noncoated ones (p = 0.0001). In this assay, i ntra-assay and inter-assay variation coefficients ranged between 4% an d 10%. Clinical evaluation showed that IgG-a-beta 2-GPI were found in 23 of 61 patients with AID but in only one patient with an infectious disease. The presence of the IgG-a-beta(2)-GPI in association with APS (p = 0.005) was statistically significant with high specificity (98%) and positive predictive value (87.5%) but with low sensitivity (54%), and was significantly associated with venous thrombosis (p = 0.0025). In addition, the IgG-a-beta(2)-GPI levels were highly correlated with those of anticardiolipin antibodies (aCL) (p < 0.001). In contrast to a-beta(2)-GPI, aCL were found with a high prevalence (40%) in patient s with infectious diseases. Because of their high specificity, anti-be ta(2)-GPI antibodies appear to be useful tools in the evaluation of th e risk of APS. However, because of their low sensitivity, their detect ion needs to be associated with that of aCL.