Abstract

Background: The risk of tuberculosis (TB) in patients with rheumatoid arthritis (RA) is thought to be increased following anti-TNF therapy, with a proposed differential risk between the anti-TNF drugs etanercept (ETA), infliximab (INF) and adalimumab (ADA). We aimed to compare directly the risk between drugs, to explore time to event, site of infection and the role of ethnicity.

Methods and findings: Using data from the British Society for Rheumatology Biologics Register (BSRBR), a national prospective observational study, we compared TB rates in 10712 anti-TNF treated patients (3913 ETA, 3295 INF, 3504 ADA) and 3232 patients with active RA treated with traditional disease-modifying anti-rheumatic drugs.

Results: To April 2008, 40 cases of TB were reported, all in the anti-TNF cohort. The rate of TB was higher for the monoclonal antibodies ADA (144 events/ 100,000 person years (pyrs)) and INF (136/100,000 pyrs) than ETA (39/ 100,000 pyrs). After adjustment, the incidence rate ratio compared to ETA-treated patients was 3.1 (95% CI 1.0, 9.5) for INF and 4.2 (1.4, 12.4) for ADA. The median time to event was lowest for INF (5.5 months) compared to ETA (13 months) and ADA (18.5 months). 13/40 cases occurred after stopping therapy. 25/40 (62%) cases were extra-pulmonary, of which 11 were disseminated. Patients of non-white ethnicity had a six-fold increased risk of TB compared to white patients treated with anti-TNF therapy.

Conclusion: The rate of TB in patients with RA treated with anti-TNF therapy was 3-4 fold higher in patients receiving INF and ADA compared to ETA.