Antibiotic treatment and flares of rheumatoid arthritis: a self-controlled case series study analysis using CPRD GOLD.

There is emerging evidence of the impact of infections on rheumatoid arthritis pathogenesis and flares. We aimed to study the association between antibiotic use (and timing of use), and the occurrence of flares in patients with RA. We nested a self-controlled case series (SCCS) of patients who have RA flares within a newly diagnosed RA cohort (n = 31,992) from the UK Clinical Practice Research Datalink (CPRD) GOLD dataset. We determined associations between exposure to antibiotics (beta-lactam, imidazole, macrolide, nitrofurantoin, quinolone, sulphonamide and trimethoprim, and tetracycline) and the occurrence of RA flares. Conditional fixed-effects Poisson regression models were used to determine incidence rate ratios (IRR), offset by the natural logarithm of risk periods. A total of 1,192 (3.7%) of RA subjects had one or more flare/s during the study period, and were therefore included. Use of sulphonamide and trimethoprim was associated with an increased risk of RA flare at 29-90 days (IRR 1.71, CI 1.12-2.59, p = 0.012); 91-183 days (IRR 1.57, CI 1.06-2.33, p = 0.025); and 184-365 days (IRR 1.44, CI 1.03-2.02, p = 0.033) after commencement of antibiotic treatment. No other antibiotic group/s appear associated with RA flare/s risk. Usage of sulphonamide and trimethoprim antibiotics, is associated with a 70% increased risk of RA flare at 1-3 months, which decreases but remains significant up to 12 months after treatment. We hypothesise that the delayed onset of RA flares after specific antibiotics is mediated through the gut or urinary microbiomes. Further epidemiological and mechanistic research is needed to determine the role of infections in RA.