Factors associated with structural progression of the sacroiliac joints on MRI in axial spondyloarthritis: a retrospective longitudinal study.

PURPOSE: To identify clinical and routine sacroiliac joint (SIJ) MRI variables associated with structural damage progression in axial spondyloarthritis (axSpA).

MATERIALS AND

METHODS

This retrospective longitudinal study enrolled 234 patients with axSpA who underwent at least two SIJ MRI examinations between August 2011 and March 2024 (643 examinations, 409 consecutive visit pairs). Progression at each follow-up examination relative to the previous one was adjudicated using an SSS-based three-step algorithm. Mixed-effects logistic regression with patient-specific random intercepts identified factors associated with progression, with the MRI follow-up interval as a covariate. Multicollinearity was assessed using variance inflation factors, and treatment exposure was evaluated in a sensitivity analysis.

RESULTS

Progression was identified in 260 of 409 follow-up examinations (63.6%). After adjustment for the MRI follow-up interval, a higher erosion SSS score (odds ratio [OR] 1.178, 95% confidence interval [CI] 1.099-1.262, P < 0.001), smoking (OR 2.023, 95% CI 1.091-3.751, P = 0.025), and HLA-B27 positivity (OR 2.929, 95% CI 1.225-7.007, P = 0.016) were independently associated with increased progression risk, whereas older age at diagnosis (OR 0.970, 95% CI 0.946-0.993, P = 0.012) was associated with decreased risk; these associations were essentially unchanged after forced entry of treatment exposure.

CONCLUSION

A higher erosion burden at the previous examination, smoking, and HLA-B27 positivity were associated with SIJ structural damage progression; patients diagnosed at a younger age also warrant attention. Given the retrospective observational design, these are statistical associations whose causality and clinical utility require prospective validation.