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.