HLA-B27 Frequency and Clinical Correlates in Turkish Patients with Various Subtypes of Spondyloarthritis: A Single-Center Cohort Study

Aim: This study aimed to evaluate the frequency of human leukocyte antigen (HLA)-B27 positivity and its clinical correlations in Turkish patients with ankylosing spondylitis (AS), psoriatic arthritis (PsA), inflammatory bowel disease (IBD)-associated arthritis, peripheral spondyloarthritis (pSpA), and non-radiographic axial SpA (nr-axSpA). Materials and Methods: In this retrospective single-center cohort study, data from 524 AS, 380 PsA, 28 IBD-associated SpA, 45 pSpA, and 236 nr-axSpA patients were analyzed. Clinical features, HLA-B27 status, inflammatory markers, and imaging results were collected. Statistical analyses included the Chi-square tests, the Mann-Whitney U tests, Spearman’s rank correlations, and logistic regression. Results: HLA-B27 positivity was detected in 58.2% AS, 31.1% PsA, 25.0% IBD-SpA, 40.0% pSpA, and 35.2% nr-axSpA patients. In AS, HLA-B27 positivity correlated with higher C-reactive protein levels (p=0.001), elevated bath AS disease activity index (BASDAI) (p=0.0234), and bath ankylosing spondylitis functional index (BASFI) (p=0.0207) scores, male sex (p=0.0017), and younger age at onset (p=0.034). In PsA, higher PsA disease activity score were significantly associated with HLA-B27 positivity (p<0.0001). For IBD-SpA, HLA-B27 positivity correlated with younger age at disease onset (p=0.016), increased BASDAI (p=0.0003), and BASFI (p=0.0004). In nr-axSpA, male sex (p=0.00015), elevated BASDAI (p<0.0001), BASFI (p<0.0001), and increased biologic usage (p=0.0277) were significantly associated with HLA-B27 positivity, while non-steroidal anti-inflammatory drug responsiveness was higher in negatives (p=0.0058). Magnetic resonance imaging sacroiliitis negatively correlated with HLA-B27 positivity in AS (rho=-0.140, p=0.002). Conclusion: HLA-B27 positivity varies across SpA subtypes, significantly correlating with male sex, disease activity, and functional impairment scores in axial SpA groups, with the highest prevalence in AS. While certain associations with disease activity and treatment patterns were observed, the overall clinical impact of HLA-B27 was limited. These findings highlight the complex and heterogeneous nature of HLA-B27’s role in SpA and emphasize the need for further prospective studies to clarify its prognostic significance.