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 rheumatoid arthritis (RA), psoriatic arthritis (PsA), or ankylosing spondylitis/spondyloarthritis (AS/SpA) from 2010 through 2018. For each IA patient, we randomly sampled ten 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 = 5,988; AS/SpA, n = 6,386) and 285 040 BP individuals. The one-year prevalence of any antibiotic dispensing was 42.1% in IA patients before diagnosis vs 30.7% in the BP. The total antibiotic dispensing was higher the one-year before both RA, PsA, and As/SpA compared with BP (prevalence rate ratios [PRR], 1.48 [1.46; 1.51]; 1.67 [1.62; 1.72]; 1.52 [1.47; 1.56], respectively), and 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 utilisation patterns change after IA diagnosis with marked differences among IA subgroups.