Clinical characteristics of non-radiographic versus radiographic axial spondyloarthritis in Asia and non-radiographic axial spondyloarthritis in other regions: results of the cross-sectional ASAS-COMOSPA study

OBJECTIVES: To delineate characteristics of non-radiographic axial spondyloarthritis (nr-axSpA) in Asia versus non-Asian regions, and compare radiographic axSpA (r-axSpA) with nr-axSpA within Asia. METHODS: Data were collected from the Assessment of SpondyloArthritis international Society-COMOrbidities in SPondyloArthritis database. Categorising patients by region, we compared clinical characteristics between nr-axSpA from Asia vs elsewhere (Europe, the Americas and Africa). Within Asians, we additionally compared patient characteristics of those with nr-axSpA versus r-axSpA. RESULTS: Among 3984 SpA cases, 1094 were from Asian countries. Of 780 axSpA patients in Asia, 112 (14.4%) had nr-axSpA, less than in non-Asian countries (486/1997, 24.3%). Nr-axSpA patients in Asia were predominantly male (75.9% vs 47.1%), younger at onset (22.8 vs 27.8 years) and diagnosis (27.2 vs 34.5 years), and experienced less diagnostic delay (1.9 vs 2.9 years) compared with nr-axSpA in non-Asian countries. Nr-axSpA in Asia exhibited higher human leucocyte antigens-B27 prevalence (90.6% vs 61.9%), fewer peripheral SpA features (53.6% vs 66.3%) and similar extra-articular and comorbid disease rates compared with those with nr-axSpA in non-Asian countries. Disease activity, functional impairment and MRI sacroiliitis were less in nr-axSpA in Asia, with higher rates of non-steroidal anti-inflammatory drug response and less methotrexate and biological disease-modifying antirheumatic drugs use. Within Asia, r-axSpA showed higher disease activity and structural damage compared with nr-axSpA, with no differences in other features. CONCLUSION: Among axSpA, lower frequency of nr-axSpA was observed in Asia. Our results offer an opportunity to better understand clinical characteristics and optimise diagnostic strategies, such as ensuring access and availability of MRI resources for accurate diagnosis of nr-axSpA in Asia.