Radiographic Progression in Sacroiliac Joints in Patients With Axial Spondyloarthritis: Results From a Five‐Year International Observational Study

Objective To evaluate progression from nonradiographic (nr‐) to radiographic axial spondyloarthritis (r‐axSpA) over 5 years in patients with recently diagnosed (≤1 year) axSpA fulfilling the Assessment of SpondyloArthritis international Society (ASAS) classification criteria. Methods A prospsective, observational study (Patients with Axial Spondyloarthritis: Multi‐Country Registry of Clinical Characteristics) was conducted in rheumatology practices in 29 countries. Baseline and follow‐up radiographs of sacroiliac joints were centrally evaluated by three readers according to the grading system of the modified New York criteria for patients initially classified as nr‐axSpA. Radiographic progression from nr‐axSpA to r‐axSpA was evaluated by Kaplan‐Meier analysis. Cox proportional regression analyses for progression from nr‐axSpA to r‐axSpA were also conducted. Results Among 2,165 patients with axSpA, 1,612 (74%) were classified as having r‐axSpA (1,050 [65%]) or nr‐axSpA (562 [35%]) by central reading. Of 246 patients with nr‐axSpA (mean [SD] symptom duration: 4.4 [6.2] years) who had at least one follow‐up sacroiliac joint radiograph, progression from nr‐axSpA to r‐axSpA at any follow‐up visit was observed in 40 patients (16%) over 5 years. Mean time to radiographic progression was 2.4 years (ranging from 0.9 to 5.1 years). Progression to r‐axSpA was associated with male sex (hazard ratio [HR] 3.16 [95% CI 1.22–8.17]), fulfillment of the imaging arm of the ASAS classification criteria (HR 6.64 [1.37–32.25]), and good response to nonsteroidal anti‐inflammatory drugs (HR 4.66 [1.23–17.71]). Conclusion 16% of patients with nr‐axSpA progressed to r‐axSpA within 5 years. Male sex, fulfillment of the imaging arm of the ASAS criteria, and good response to nonsteroidal anti‐inflammatory drugs were predictors of radiographic progression in patients with recently diagnosed axSpA.