Incidence and Risk of Infections in Patients With Radiographic Axial Spondyloarthritis Receiving Biologic Therapies: A Prospective Observational Study Using the KOBIO Registry

Objective This study aimed to assess the occurrence of infection and risk factors among patients with radiographic axial spondyloarthritis (r-axSpA) treated with biologics in a real-world setting.

Methods This prospective observational cohort study included patients with r-axSpA from the Korean College of Rheumatology Biologics (KOBIO) registry who initiated or switched to a biologic agent between December 2012 and December 2023. The primary outcome was the first occurrence of any infection, ranging from mild to severe, classified by organ system. The infection rates per 1000 person-years (PY), with 95% CI, were calculated using the Poisson distribution method. Cox proportional hazard regression models—adjusted for confounders—estimated hazard ratios for infection risk, considering only the first infection event.

Results This analysis included 2129 patients with a total of 7107.67 PY of follow-up. The predominant infections observed were of the upper and lower respiratory tract (25.89/1000 PY), followed by herpes zoster (HZ; 6.13/1000 PY). Multivariate Cox regression analysis revealed significant risk factors for infection, including advanced age, ischemic heart disease (IHD), diabetes mellitus (DM) with complications, chronic kidney disease (CKD), and peripheral arthritis. In contrast, male sex was identified as a protective factor against the development of infections.

Conclusion The infection rate was 39.39 events/1000 PY, with respiratory tract infections being most common, followed by HZ. Significant risk factors for the occurrence of infection in patients with r-axSpA treated with biologics included advanced age, female sex, IHD, DM with complications, CKD, and peripheral arthritis. These findings emphasize infection risk assessment, particularly in high-risk patients, to optimize the safety of biologic therapy in r-axSpA.