Antibiotics in inflammatory arthritis and background population one year before and after diagnosis: a nationwide drug utilisation study

Objectives: To describe antibiotic use in patients with inflammatory arthritis (IA) and in the background population (BP) within one year before and after IA diagnosis. Methods: Using data from Danish nationwide registries, we identified all adults with a first-time diagnosis of RA, PsA, or AS/spondyloarthritis (AS/SpA) from 2010 through 2018. For each IA patient, we randomly sampled 10 persons from the BP, matched on sex and birthdate. We calculated the prevalence (n %) of any antibiotic dispensing and the total antibiotic dispensing in the year before and after diagnosis. Results: We identified 28 504 new-onset IA patients (RA, n 16 130; PsA, n 5988; AS/SpA, n 6386) and 285 040 BP individuals. Within one year before diagnosis, the total amount of dispensed antibiotics was higher in both RA, PsA and As/SpA compared with the BP (prevalence rate ratios PRR, 1.48 1.46; 1.51; 1.67 1.62; 1.72; 1.52 1.47; 1.56, respectively). The amount increased with 22% in IA patients three months before diagnosis compared with the preceding three-month period. Although the prevalence of any antibiotic dispensing in IA patients decreased in the year following the diagnosis (IA; 40.6%), the total one-year antibiotic dispensing remained constant in RA (PRR 0.99 0.97; 1.01), decreased in PsA (0.91 0.87; 0.94) and increased in AS/SpA (1.08 1.04; 1.12) patients after diagnosis compared with before. Conclusion: Antibiotics are more frequently dispensed to individuals developing IA compared with the BP. Antibiotic utilization patterns change after IA diagnosis with marked differences among IA subgroups.