Serious infection across biologic-treated patients with rheumatoid arthritis: results from the British Society for Rheumatology Biologics Register for Rheumatoid Arthritis.

The rate of SI was lower with certolizumab pegol than etanercept in the primary analysis but the result was no longer significant in several sensitivity analyses performed suggesting residual confounding may account for the observed difference. From these results, it would be wrong to conclude that certolizumab pegol has a lower rate of SI than other biologics; however, the risk does not appear to be significantly higher as has previously been suggested.