Antimicrobial Use and Serious Infections Among Patients With Psoriatic Arthritis After Initiating Tumor Necrosis Factor Inhibitors: A Nationwide Matched Cohort Study

Objective To analyze antimicrobial use and serious infections (SI) among patients with psoriatic arthritis (PsA) before and after initiating tumor necrosis factor inhibitor (TNFi) treatment.

Methods In this nationwide matched cohort study, we extracted data on patients with PsA initiating TNFi from 2005 to 2018 from the ICEBIO registry and matched them by age, sex, and calendar time to 5 randomly selected comparators from the general population. All filled prescriptions for antimicrobials, glucocorticoids, and methotrexate 2 years before and after initiating TNFi treatment were extracted from the Icelandic Prescription Medicines Register. All infection-related hospitalizations, a proxy for SI, were extracted from the Icelandic Hospital Discharge Register.

Results The study included 399 PsA patients and 1986 matched comparators. Patients received more antimicrobial prescriptions before TNFi treatment, with a mean number of prescriptions per year of 1.26 vs 0.60 (P < 0.001). The mean number of prescriptions increased to 1.64 (P < 0.001) in the 12 months following TNFi initiation but returned to baseline thereafter. No statistically significant increase in SI was found. Adjusted for covariates, patients with PsA had a hazard ratio of 1.43 (95% CI 1.18-1.72, P < 0.001) for receiving a prescription for antimicrobials following TNFi treatment initiation compared to before TNFi treatment. The risk was increased in the first year after treatment initiation but not in the second year, suggesting a transient effect.

Conclusion Following TNFi initiation, antimicrobial use rose temporarily, with no significant increase in SI. These results support the safety of TNFi in PsA management, and the risk of SI should not weigh heavily in treatment decisions.