Objectives: The degree to which treatment with TNF-antagonists may be associated with increased risks for serious infections is unclear. We performed an observational cohort study using prospectively collected data from the Swedish Biologics Register (ARTIS) and other national Swedish registers.
Methods First, in the Swedish biologics register (ARTIS) we identified all 4,167 RA-patients starting TNF- antagonist treatment between 1999 and 2003. Second, in the Swedish Inpatient Register, we identified all individuals hospitalized for any reason and who also carried a diagnosis of RA, between 1964 and 2003 (n=44,946 of whom 2,692 also occurred in ARTIS). Thirdly, in the Swedish Inpatient Register, we identified all hospitalisations listing an infection between 1999 and 2003. By cross-referencing these three data-sets, we calculated relative risks (RR) for hospitalisation with infection associated with TNF- antagonist treatment within the cohort of 44,946 RA patients, using Cox regression taking age sex, age, geography, co-morbidity, and use of inpatient care into account.
Results Among the 4,167 patients treated with TNF- antagonists, 367 hospitalizations with infections occurred during 7,776 person-years. Within the cohort of 44,496 RA patients, the relative risk for infection associated with TNF-antagonists was 1.43 (95%CI 1.18- 1.73) during the first year of treatment, 1.15 (95% CI 0.88-1.51) during the second year of treatment, and 0.82 (95% CI 0.62-1.08) for subjects remaining on their first TNF-antagonist treatment after two years.
Conclusion Treatment with TNF-antagonists may be associated with a small to moderate increase in risk of hospitalization with infection, which disappears with increasing treatment duration.
- rheumatoid arthritis