Disease course of non-radiographic axial spondyloarthritis: Data from a long-term retrospective observational cohort

BACKGROUND: Disease course of non-radiographic axial spondyloarthritis (axSpA) has been extensively studied in non-Asian population; however, there are limited data in Asian population. This study aimed to evaluate the long-term disease course of non-radiographic axSpA in Asian patients and identify factors associated with progression to radiographic axSpA. METHODS: In this retrospective observational cohort study, 56 Korean patients newly diagnosed with non-radiographic axSpA between 2006 and 2015 were included. All patients fulfilled the Assessment of SpondyloArthritis international Society classification criteria for axSpA, and did not fulfil the radiological criterion of the 1984 modified New York criteria. Disease course was assessed by the rate of progression to radiographic axSpA. Factors associated with the risk of progression to radiographic axSpA were assessed using multivariable Cox proportional hazard regression analysis. RESULTS: The mean age at baseline was 31.4±13.3 years, and 37 (66.1%) patients were men. Over a mean observation period of 8.4±3.7 years, 28 (50.0%) patients progressed to radiographic axSpA. In multivariable Cox proportional hazard regression analysis, the presence of syndesmophytes at diagnosis (adjusted hazard ratio [HR]: 4.50, 95% confidence interval [CI]: 1.54–13.15, p = 0.006) and active sacroiliitis on magnetic resonance imaging (MRI) at diagnosis (adjusted HR: 5.88, 95% CI: 2.05–16.82, p = 0.001) were significantly associated with a higher risk of progression to radiographic axSpA, whereas longer exposure to tumor necrosis factor inhibitors (TNFis) was significantly associated with a lower risk of progression to radiographic axSpA (adjusted HR: 0.89, 95% CI: 0.80–0.98, p = 0.022). CONCLUSION: During long-term follow-up, a substantial proportion of Asian patients with non-radiographic axSpA progressed to radiographic axSpA. The presence of syndesmophytes and active sacroiliitis on MRI at the time of non-radiographic axSpA diagnosis were associated with a higher risk of progression to radiographic axSpA, while longer exposure to TNFis was associated with a lower risk of progression to radiographic axSpA.