Axial SpA manifestations, disease activity vary widely across geographic regions
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Patients with axial spondyloarthritis demonstrate significant differences in peripheral and extra-musculoskeletal manifestations based on geographic region, according to data published in Rheumatology.
“The most frequent [axial SpA (axSpA)] symptom is chronic, often inflammatory back pain that might be difficult to distinguish from other causes of chronic back pain (CBP),” Denis Poddubnyy, MD, MSc, of Charité-Universitätsmedizin Berlin, and colleagues wrote. “Other musculoskeletal manifestations of axSpA include peripheral arthritis, enthesitis and, less frequently, dactylitis. AxSpA may also present with extra-musculoskeletal manifestations (EMMs), such as psoriasis, uveitis and IBD.”
“The classification of axSpA patients into [radiographic axSpA (r-axSpA)] and [non-radiographic axSpA (nr-axSpA)] is based on the presence or absence of radiographic sacroiliitis (according to the radiographic criterion of the modified New York criteria for AS) on plain pelvic radiographs,” they added. “In studies of patients with newly diagnosed axSpA, 23-80% were classified as having nr-axSpA, which is substantially dependent on the disease duration at the time of diagnosis.”
To compare the demographic and clinical characteristics of patients with axial SpA across geographic regions, Poddubnyy and colleagues reported on baseline data from the Patients with Axial Spondyloarthritis: Multi-country Registry of Clinical Characteristics (PROOF) study. According to the researchers, PROOF is an observational study that recruited 2,170 patients recently diagnosed — within 1 year of enrollment — with axial SpA between Jan. 27, 2014, and Aug. 30, 2015. Participants resided in 29 countries across various regions in Africa, Asia, Europe, North America and South America.
For this study, Poddubnyy and colleagues reported on 1,553 participants who were classified as having radiographic or non-radiographic axial SpA, based on central evaluation of sacroiliac radiographs. Among these patients, 1,023 were radiographic and 530 were non-radiographic.
According to the researchers, patients with non-radiographic axial SpA demonstrated a significantly higher occurrence of enthesitis — 40% versus 33% — psoriasis — 10% versus 5% — and inflammatory bowel disease (IBD) — 4% versus 2% — compared with radiographic individuals.
In addition, the researchers reported significant differences in disease characteristics between geographic regions. For example, the highest occurrences of peripheral arthritis, enthesitis and dactylitis were in Latin America, with 60%, 52% and 12%, respectively. Meanwhile, the lowest occurrences were in Canada, with 9%, 9% and 2%, respectively. Uveitis and psoriasis occurrences were highest in Canada, at 18% and 14%, respectively, and lowest in China, at 6% and less than 1%, respectively. IBD, meanwhile, was highest in the Arabian Peninsula, at 21%, while no cases were reported in China.
In their multivariable analysis, adjusting for factors that may impact peripheral and extra-musculoskeletal manifestations, the researchers still found that geographic regions exhibited significant differences in the frequencies of uveitis (P<.01), psoriasis (P<.0001) and peripheral arthritis (P<.0001).
“The baseline data provided novel insights into the differences in the clinical presentation of axSpA across various geographic regions,” Poddubnyy and colleagues wrote. “Most notably, patients in Latin America had the highest frequencies of peripheral arthritis, enthesitis and dactylitis, while patients in China had the lowest disease activity, including a low occurrence of peripheral manifestations and EMMs. These data may inform management patterns and the planning of interventional clinical trials.”
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