Antibodies to domain I β2 -glycoprotein 1 in patients with antiphospholipid syndrome and systemic lupus erythematosus

Abstract

The study of antiphospholipid antibodies (aPL), not included in the Sydney diagnostic criteria, in antiphospholipid syndrome (APS) and systemic lupus erythematosus (SLE) is poorly understood.The aim of this study – to determine the clinical significance of IgG antibody testing for domain I β2 -glycoprotein 1 (β2 -GP1DI) – IgG anti-β2 -GP1DI in patients with APS with and without SLE.Materials and methods. The study included 187 patients with APS with or without SLE, 49 patients formed a comparison group, and 100 relatively healthy individuals formed a control group. IgG/IgM antibodies to cardiolipin and IgG/ IgM anti-β2 -GP1 were determined by enzyme immunoassay (ELISA) in patients with or without APS, and IgG antiβ2 -GP1DI was determined by chemiluminescence assay in all patients and controls.Results. IgG anti-β2 -GP1DI was detected in 37 (71%) of 52 patients with primary APS (PAPS), in 6 (50%) of 12 patients with probable APS, in 42 (71%) of 59 patients with SLE+APS, in 17 (26%) of 64 patients with SLE, in 1 (2%) of comparison group and in none of control group. IgG anti-β2 -GP1DI was significantly associated with PAPS and SLE+APS compared with patients with SLE (p=0.0002 and p=0.0001, respectively). The association of IgG anti-β2 -GP1DI with clinical manifestations of APS (thrombosis (χ2 =9.69; p=0.001) and obstetric pathology (χ2 =4.19; p=0.04)) was detected. There was a significant association of IgG anti-β2 -GP1DI with arterial thrombosis (χ2 =8.84; p=0.002) and with late gestational obstetric pathology (χ2 =6.35; p=0.01). High specificity of IgG anti-β2 - GP1DI depending on the diagnosis and clinical manifestations of APS was noted despite low sensitivity: specificity for thrombosis was 84%, for obstetric pathology – 94%, for APS – 89%. Isolated IgG anti-β2 -GP1DI positivity was reported in 2% of 50 aPL negative patients and was not associated with APS manifestations.Conclusion. The frequency of IgG anti-β2 -GP1DI detection was higher in patients with APS compared to patients with SLE, comparison group and control (p<0.05). Positive IgG anti-β2 -GP1DI values were significantly associated with thrombotic complications and with obstetric pathology (χ2 =8.84; p=0.002 and χ2 =6.35; p=0.01). Specificity>˂ 0.05). Positive IgG anti-β2 -GP1DI values were significantly associated with thrombotic complications and with obstetric pathology (χ2 =8.84; p=0.002 and χ2 =6.35; p=0.01). Specificity of IgG anti-β2 -GP1DI for APS and its clinical manifestations (thrombosis and obstetric pathology) was higher than sensitivity: 89%, 94%, and 84%, respectively.