Clinical Characterization of Antiphospholipid Syndrome by Detection of IgG Antibodies Against β ₂ ‐Glycoprotein I Domain 1 and Domain 4/5: Ratio of Anti–Domain 1 to Anti–Domain 4/5 As a Useful New Biomarker for Antiphospholipid Syndrome

Abstract

Anti-D1 IgG is the preferential specificity not only in vascular and obstetric primary APS, but also in patients with systemic autoimmune rheumatic disease with no clinical features of APS. Conversely, aPL carriers do not have a polarized profile toward D1. Combined testing for anti-β2 GPI IgG with different domain specificity allows a more accurate aPL profiling, with polarization toward anti-D1 IgG as a possible fingerprint of systemic autoimmunity.