Beyond the Surface: Antinuclear Antibodies in Rheumatoid Arthritis-Experiences from a Single-Center, Cross-Sectional Observational Study.

Abstract

Background: Antinuclear antibodies (ANA) can be detected in patients with rheumatoid arthritis (RA) and pose many diagnostic challenges, especially when RA presents an atypical course and requires differentiation from other systemic connective tissue diseases (sCTDs). This study assessed ANA fluorescence patterns and immunoblot profiles, as well as the relationships between ANA titers, antibody expression intensity, and markers of disease activity in patients with RA. Methods: This single-center, cross-sectional, observational study included 81 RA patients (53 ANA-positive) meeting the 2010 ACR/EULAR classification criteria. ANA titers and fluorescence patterns were assessed using indirect immunofluorescence. Anti-extractable nuclear antigen (ENA) autoantibody profiles and expression intensity were assessed using immunoblot analysis. Demographic, clinical, and laboratory data were obtained. Spearman's rank correlation coefficient was used to analyze the relationship between ANA titers and selected variables. Univariate and multivariate logistic regression analyses were performed to identify factors associated with ANA positivity. Results: The cohort consisted primarily of women (86.4%) with moderate disease activity. ANA fluorescence patterns were heterogeneous, with nucleolar and homogeneous patterns most frequently observed. Immunoblot analysis also revealed diverse autoantibody profiles without a clearly dominant specificity. Ro-52, SS-A, and Sm antibodies were detected more frequently, although their prevalence remained relatively low. No statistically significant correlations were found between ANA titers and inflammatory markers, serological parameters, or disease activity indices. Conclusions: RA patients with positive ANA demonstrated marked immunological heterogeneity, without concomitant symptoms of sCTD. A positive result in RA may reflect generalized immune dysregulation rather than a distinct clinical subtype. Further studies with larger cohorts are needed to clarify the clinical significance of ANAs in rheumatoid arthritis.