British Journal of Rheumatology 1996;35:1239-1243 SPECIFICITY OF ELISA FOR ANTIBODY TO /J2-GLYCOPROTEIN I IN PATIENTS WITH ANTIPHOSPHOLIPID SYNDROME

The clinical significance of anti-/J2 glycoprotein I (/?2-GPI) antibodies was evaluated in patients with antiphospholipid syndrome (APS), primary and secondary to systemic lupus erythematosus (SLE). Anti-/?2-GPI were tested in 120 patients (39 primary APS, 32 APS with SLE and 49 SLE without APS) by ELISA utilizing irradiated plates in the absence of cardiolipin. Anticardiolipin antibodies (aCL) and antiphosphatidylserine antibodies were also measured in the same patients using standardized assays. Anti-/?2-GPI titres correlated strongly to those of aCL (r = 0.816, P = 0.0001), and to those of antiphosphatidylserine antibodies (r = 0.841, P = 0.0001). Anti-/J2-GPI were detected in 53.5 % of APS patients (38/71), but only in 4.1 % of SLE patients without APS (2/49). In the latter group, 24.5 % (12/49) of patients had a positive titre of aCL. The anti-/32-GPI assay showed higher specificity for APS than the aCL in APS (96 vs 75%, respectively, x1 = 675> p = 0.00094). Our findings suggest that the assay of anti-/J2-GPI may improve the specificity for APS. KEY WORDS: Anticardiolipin antibody, Systemic lupus erythematosus, Thrombosis, Antiphosphatidylserine antibodies. SINCE the first study of antiphospholipid antibodies (aPL) by Wassermann, who introduced a serological test for syphilis, the family of aPL has largely expanded to include a heterogeneous group of antibodies, whose specificity is now claimed to be directed not onl