Imaging Outcomes for Axial Spondyloarthritis and Sensitivity to Change: A Five-Year Analysis of the DESIR Cohort

Objective To compare the sensitivity to change of different imaging scoring methods in patients with early axial spondyloarthritis (SpA). Methods Patients from the Devenir des Spondylarthropathies Indiffererenciees Recentes (DESIR) cohort fulfilling the Assessment of SpondyloArthritis international Society criteria for axial SpA were included. Radiographs and magnetic resonance imaging (MRI) of the sacroiliac (SI) joints and spine were obtained at baseline, 1, 2, and 5 years. Each image was scored by 2 or 3 readers in 3 separate reading waves. The rate of change of outcomes measuring inflammation of the spine and SI joints (e.g., Spondyloarthritis Research Consortium of Canada [SPARCC] score) and structural damage on MRI (e.g., >= 3 fatty lesions) and radiographs (e.g., modified New York grading) was assessed using multilevel generalized estimating equation models (taking all readers and waves into account). To allow comparisons across outcomes, rates were standardized (difference between the individual's value and the population mean divided by the SD). Results In total, 345 patients were included. Inflammation detected on MRI of the SI joints (MRI-SI joints) (standardized rate range -0.278, -0.441) was more sensitive to change compared to spinal inflammation (range -0.030, -0.055). Structural damage in the SI joints showed a higher standardized rate of change on MRI-SI joints (range 0.015, 0.274) compared to radiography of the SI joints (range 0.043, 0.126). MRI-SI joints damage defined by >= 3 fatty lesions showed the highest sensitivity to change (0.274). Spinal structural damage slowly progressed over time with no meaningful difference between radiographic (range 0.037, 0.043) and MRI structural outcomes (range 0.008, 0.027). Conclusion Structural damage assessed in pelvic radiographs has low sensitivity to change, while fatty lesions detected on MRI-SI joints are a promising alternative. In contrast, MRI of the spine is not better than radiography of the spine in detecting structural changes in patients with early axial SpA.