Tumour necrosis factor inhibitor therapy and infection risk in axial spondyloarthritis: results from a longitudinal observational cohort

OBJECTIVES: Long-term data on infection risk in axial SpA (axSpA) are sparse. TNF inhibitors (TNFis) are increasingly being used in axSpA, with infection being the most important adverse event. We aimed to investigate the frequency of infections in axSpA and to identify factors predisposing to infection. METHODS: Data were extracted from a longitudinal observational cohort of patients with axSpA. Infection rates were calculated and multivariate analysis was performed to investigate the association of independent variables with infection. RESULTS: Data were analysed for 440 patients followed for a total of 1712 patient-years (pys). A total of 259 infections, of which 23 were serious, were recorded in 185 patients. The overall rate of any infection was 15 (95% CI 13, 17)/100 pys and the serious infection rate was 1.3 (95% CI 0.9, 2.0)/100 pys. There was no significant difference in the rate of any infection or serious infection in patients on TNFis compared with patients never on biologic agents. In the multivariate analysis, DMARD treatment, but not TNFi treatment, was associated with risk of infection. Age, disease duration, smoking status, BASFI, BASDAI, co-morbidity score and hospitalization were not associated with an increased risk of infection. CONCLUSION: The serious infection rate in axSpA in this observational cohort is low when compared with rates reported in other rheumatic diseases. Biologic use was not a significant risk factor for serious infection.