Contribution of anti-β2glycoprotein I IgA antibodies to the diagnosis of anti-phospholipid syndrome: potential interest of target domains to discriminate thrombotic and non-thrombotic patients

Methods. A retrospective analysis was performed on sera from 439 patients referred for routine detection of aPL IgA by in-house ELISA. Sera positive for a beta 2GPI IgA were subsequently tested for a beta 2GPI domain 1 (D1) and domain 4/5 (D4/5) antibodies using ELISAs. Results. The prevalence of a beta 2GPI IgA antibodies was 16% in patients, significantly different from controls (1%, P < 0.0001). These antibodies were associated with clinical contexts related to APS as thrombosis (28.6% vs 15%, P = 0.009) and SLE (42% vs 15%, P < 0.0001). Interestingly, determination of their target domains revealed a significant association between a beta 2GPI IgA directed against D4/5 and SLE without thrombosis (66.7 vs 16.7%, P = 0.002). In contrast, aCL IgA were not more prevalent in patients than in controls. Conclusion. Our study confirmed the interest of a beta 2GP1 IgA in the exploration of APS and suggests that identification of target domains of a beta 2GP1 IgA may be useful in the evaluation of thrombotic risk in SLE patients.