Incidence and risk of infections in patients with ankylosing spondylitis receiving biologic therapies: A prospective observational study using the KOBIO registry.

Objective: This study aimed to assess infection occurrence of infection and risk factors among ankylosing spondylitis (AS) patients treated with biologics in a real-world setting.

Methods: This prospective observational cohort study included AS patients from the Korean College of Rheumatology BIOlogics (KOBIO) registry who initiated or switched to biologic agent between December 2012 and July 2023. The primary outcome was the first occurrence of any infection, ranging from mild to severe, classified by organ system. The infection rate per 1,000 person-years (PY), with a 95% confidence interval 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 2,129 patients with a total of 7,107.67 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 age, ischemic heart disease, complicated diabetes, 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 events/1,000 PY with respiratory tract infections being most common, followed by HZ. Significant risk factors included age, female sex, ischemic heart disease, complicated diabetes, CKD and peripheral arthritis for the occurrence of infection in patients with AS treated with biologics.