Detection of IgG anti-Domain I beta2 Glycoprotein I antibodies by chemiluminescence immunoassay in primary antiphospholipid syndrome

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BackgroundIgG anti-Domain I (anti-DI) β2 Glycoprotein I (β2GPI) antibodies are associated to thrombotic risk in antiphospholipid syndrome (APS), but their detection is technically difficult. In this study, a chemiluminescent immunoassay (CLIA) was used to evaluate the clinical significance of IgG anti-DI in a large cohort of patients with primary APS (PAPS). MethodsThe study population included 88 patients with PAPS, 63 ELISA-negative subjects and 166 controls. IgG anti-DI, IgG anticardiolipin (aCL) and IgG anti-β2GPI antibodies were assayed using CLIA (HemosIL AcuStar®). ResultsThe sensitivity and specificity of IgG anti-DI antibodies were comparable to those of IgG aCL and IgG anti-β2GPI antibodies. There was a significant agreement, association and titre correlation between IgG anti-DI and IgG aCL as well as IgG anti-β2GPI antibodies (p<0.001 for all). IgG anti-DI antibody showed lesser prevalence and mean titres in the pregnancy morbidity than in thrombotic and PAPS patients with both involvements (p<0.001). Regarding the conventional aPL antibody profiles, the triple positivity group had higher prevalence and mean titres than single and double positivity ones (p<0.001). ConclusionsThis study provides further evidence that anti-DI antibodies can be considered a promising biomarker for risk assessment particularly in patients having vascular thrombosis and triple conventional aPL positivity.