The association of serum beta-2-microglobulin with autoantibody production and disease activity in patients with primary Sjögren’s syndrome

Abstract

Aims: The aim of the this study is to evaluate beta-2-microglobulin (B2M) levels in patients with primary Sjögren’s syndrome (pSS) and to investigate their correlation with serum biomarkers and disease activity indexes commonly used in daily clinical practice.Methods: Eighty-one patients with pSS were included in this retrospective and cross-sectional study. Demographic data, clinical characteristics, B2M, immunoglobulin (Ig) A, IgG, IgM, erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), serum complement (C) 3 and C4 levels, anti-nuclear antibody, rheumatoid factor (RF), anti-SSA and anti-SSB antibodies were obtained from the medical records. Disease activity was evaluated by the European League Against Rheumatism (EULAR) SS Disease Activity Index (ESSDAI) and EULAR SS Patients Reported Index (ESSPRI). Results: Serum B2M level was significantly higher in patients with anti-SSA and anti-SSB antibody (median: 2.64 mg/dL, minimum: 2.02 mg/dL, maximum: 10.10 mg/dL) than in only anti-SSA positive patients (median: 2.31 mg/dL, minimum: 1.33 mg/dL, maximum: 4.26 mg/dL, p=0.010) and both antibody negative patients (median: 1.80 mg/dL, minimum: 1.20 mg/dL, maximum: 2.65 mg/dL, p<0.001). Also, patients with anti-SSA antibody have significantly higher serum B2M levels than anti-SSA and anti-SSB antibodies negative patients (p=0.009). Serum B2M level was significantly correlated with ESSDAI (r=0.482, p=0.001), serum IgG level (r=0.374, p=0.001), IgA level (r=0.341, p=0.002), RF levels (r=0.412, p=0.021) and ESR (r=0.239, p:0.031). There was no correlation between ESSPRI, IgM, CRP and serum B2M levels. ESSDAI was not correlated with C3 (r=0.044, p=0.697), C4 (r=-0.053, p=0.640), ESR (r=0.111, p=0.326), CRP (r=0.111, p=0.324) and IgG (r=0.154, p=0.169).Conclusions: Although serum B2M levels were higher in autoantibody positive patients, it has a weak correlation with clinical disease activity.