Anti-β2-Glycoprotein I antibodies in pediatric systemic lupus erythematosus and antiphospholipid syndrome

Objective To determine whether serum β2-glycoprotein I antibody (anti-β2GPI) detection improves identification of pediatric subjects at risk for antiphospholipid syndrome (APS). Methods Serum antiphospholipid antibodies (aPL) were identified by anticardiolipin enzyme-linked immunosorbent assay (ELISA), lupus anticoagulant assays, and syphilis screening in children with primary APS, systemic lupus erythematosus (SLE), or SLE plus APS. Anti-β2GPI level and isotype were determined by β2GPI ELISA and correlated with clinical manifestations and other aPL assays. Results One hundred-ten subjects under 22 years of age and of mixed ethnicity were evaluated. Fifty-seven had SLE (including 14 with APS), 25 had primary APS, 16 had SLE-like APS, 6 were healthy children with aPL detected incidentally, 4 had other rheumatic diseases and 2 had other conditions. Anti-β2GPI were detected in 48% of SLE subjects and did not improve aPL detection over standard tests. Anti-β2GPI were associated with stroke (P = 0.014), but not with other APS manifestations, and were rarely detected in primary APS. Among subjects with APS manifesting as chronic thrombocytopenia, anti-β2GPI distinguished subjects with SLE from those with primary APS. Conclusions With the exception of stroke, anti-β2GPI detection does not improve identification of pediatric APS over that of traditional aPL assays. Anti-β2GPI are rare in pediatric primary APS, but may predict evolution of chronic thrombocytopenia to SLE.