Characteristics of Patients With Axial Spondyloarthritis by Geographic Regions: PROOF Multicountry Observational Study Baseline Results

Abstract

To compare demographic and clinical characteristics of patients with axial spondyloarthritis (axSpA) across geographic regions.

Methods: PROOF is an observational study that enrolled recently diagnosed (≤1 year) axSpA patients fulfilling the Assessment of SpondyloArthritis international Society classification criteria from rheumatology clinical practices in 29 countries across 6 geographic regions. Demographics and disease-related parameters were collected. Here we present baseline data for patients who had classification as radiographic (r-)axSpA or non-radiographic (nr-axSpA) confirmed by central reading.

Results: Of the 2170 patients enrolled, 1553 were classified based on central evaluation of sacroiliac radiographs (r-axSpA: 1023 [66%]; nr-axSpA: 530 [34%]). Patients with nr-axSpA had significantly higher occurrence of enthesitis (40% vs 33%), psoriasis (10% vs 5%), and inflammatory bowel disease (IBD, 4% vs 2%) vs r-axSpA patients. Significant differences in axSpA characteristics were observed between geographic regions. The highest occurrence of peripheral arthritis (60%), enthesitis (52%), and dactylitis (12%) was in Latin America and the lowest in Canada (9%, 9%, and 2% respectively). Occurrence of uveitis (18%) and psoriasis (14%) was highest in Canada and lowest in China (6% and <1%). IBD was highest in Arabia (21%); no cases were observed in China. In multivariable analysis adjusted for factors potentially affecting peripheral and extra-musculoskeletal manifestations, geographic regions still exhibited significant differences in frequencies of uveitis (p<0.01), psoriasis (p<0.0001) and peripheral arthritis (p<0.0001).

Conclusions: The multinational PROOF study of axSpA patients showed significant regional differences in peripheral and extra-musculoskeletal manifestations of SpA, which could be considered in management guidelines and clinical trials.