The comparative risk of serious infections among rheumatoid arthritis patients starting or switching biological agents

Background It is unclear whether anti-tumour necrosis factor alpha and biological agents with different mechanisms of action have similar safety. This study evaluated the incidence of hospitalised infections among rheumatoid arthritis (RA) patients starting or switching various biological agents. Methods Using a database from a large US healthcare organisation from January 2005 to August 2009, the authors identified enrollees with RA and their treatment episodes entailing the new use of a biological agent, stratified by no biological use in the previous year (‘biological-free’) or switching from a different biological agent (‘switchers’). Outcomes were hospitalised infections identified using previously validated algorithms. Proportional hazards models estimated the hazard ratio of hospitalised infections, comparing each biological agent with infliximab. Results Among 7847 biological treatment episodes, 63% were for biological-free patients and 37% for switchers. There were 364 hospitalised infections. Rates of hospitalised infection among biological-free patients and switchers were 4.6 and 7.0 per 100 person-years, respectively (p