Clinical expression of radiographic axial spondyloarthritis and its association with HLA-B27 in European and Ibero-American populations.

Abstract

OBJECTIVE To compare the clinical and sociodemographic characteristics of Ibero-American patients with radiographic axial spondyloarthritis (r-axSpA) to those of European patients, with a particular focus on the influence of HLA-B27. METHODS This was an observational, cross-sectional, and multicentre study of patients who fulfilled the European Spondyloarthropathy Study Group (ESSG) criteria for SpA from the REGISPONSER and RESPONDIA registries. Univariate and multivariate analyses between European and Ibero-American populations stratified by HLA-B27 status were conducted. Race stratification (White, Black American, and Indian American) was also performed to evaluate clinical differences according to HLA-B27. RESULTS A total of 2592 patients with a clinical diagnosis of r-axSpA were included in the analysis: 1083 (41.8%) Ibero-American patients and 1509 (58.2%) European patients. Among the HLA-B27-positive patients, Ibero-American status was independently associated with conventional synthetic disease-modifying antirheumatic drugs (csDMARD) intake (OR: 4.21), arthritis (OR: 2.36), enthesitis (OR: 6.01), dactylitis (OR: 6.10), severe structural damage (BASRI) (OR: 1.12) and poor functionality (BASFI) (OR: 1.40). Multivariate analysis of HLAB27-negative patients revealed that Ibero-American status was independently associated with enthesitis (OR: 11.67), csDMARDs (OR: 15.51) and total BASRI (OR: 1.34). Clinical manifestations also varied across racial groups, with differences noted in the prevalence of peripheral joint manifestations such as more arthritis and enthesitis in American Indian patients than in White and Black American patients. CONCLUSION Ibero-American r-axSpA patients in our study exhibit more peripheral manifestations, more structural damage, and worse functionality than European patients, regardless of the presence of HLA-B27.