Risk of infection associated with subsequent biologic use after rituximab: Results from a national rheumatoid arthritis patient registry.

Objective. To assess whether the time between the last rituximab infusion and initiation of a different biologic agent influenced infection risk in patients with rheumatoid arthritis (RA). Methods. Patients with RA who newly initiated rituximab within the Consortium of Rheumatology Researchers of North America registry were included if they switched to a nonrituximab biologic agent and had >= 1 followup visit within 12 months of switching. Patients were categorized by duration of time between their last rituximab infusion and initiation of a subsequent biologic agent (<= 5 months, 6-11 months, and >= 12 months). The primary outcome was time to first infectious event. Adjusted Cox regression models estimated the association between time to starting a subsequent biologic agent and infection. Results. A total of 44 overall infections (7 serious, 37 nonserious) were reported during the 12-month followup in the 215 patients included in this analysis (104 switched at <= 5 months, 67 at 6-11 months, and 44 at >= 12 months). Median (interquartile range) time to infection was 4 (2-5) months. Infection rates per patient-year in the <= 5-month, 6-11-month, and >= 12-month groups were 0.34 (95% confidence interval [95% CI] 0.22-0.52), 0.30 (95% CI 0.17-0.52), and 0.41 (95% CI 0.22-0.77), respectively. After adjustment, time to switch to a subsequent biologic agent was not associated with infection, which remained unchanged when number and rate of rituximab retreatments were included in the models. Conclusion. In this real-world cohort of patients with RA, infection rates ranged from 0.30 to 0.41 per patient-year, with no significant difference in the rate between patients who initiated a subsequent biologic agent earlier versus later after rituximab treatment.