Uveitis in Longstanding Axial Spondyloarthritis and Its Association with Biologic Therapy Initiation: Data from the REGISPON-3 Cohort

<b>Objectives</b>: To assess the incidence rate of anterior acute uveitis (AAU) in patients with longstanding axial spondyloarthritis (axSpA); to evaluate demographic and clinical characteristics associated with AAU development; and to determine the influence of AAU on bDMARD initiation and retention in this population. <b>Methods</b>: This two-timepoint cohort study analysed data from patients enrolled in the Spanish SpA registry REGISPONSER (2004-2007), who were re-evaluated 17 years later in the REGISPON-3 follow-up study (2021-2023). Information on the date of first AAU episode and bDMARD initiation was collected. Kaplan-Meier and Cox proportional hazards models were used to assess AAU incidence, predictors, and its association with time to bDMARD initiation and treatment retention. <b>Results</b>: A total of 299 patients with longstanding axSpA were included, of whom 33.4% experienced at least one episode of AAU, corresponding to an incidence rate of 1.15 per 100 person-years. The cumulative probability of a first episode of AAU increased with disease duration. The relative risk for developing a second episode after the first, compared to the overall risk of any episode in the total population, was 1.85 (95% CI: 1.34-2.57). In multivariable cox analysis, female sex and baseline enthesitis were independently associated with a higher risk of AAU. AAU did not significantly affect the likelihood of subsequent bDMARD initiation, with similar cumulative treatment probabilities in patients with and without AAU. Among treated patients, adalimumab was more frequently prescribed in those with a history of AAU. bDMARD retention rates at two and five years were comparable regardless of AAU status, suggesting that AAU was not associated with long-term treatment persistence. <b>Conclusions</b>: In patients with longstanding axSpA, the incidence of AAU increased steadily over time. However, the presence of AAU did not significantly influence bDMARD initiation or long-term retention in routine clinical practice.