P353 Optimal Interval for Therapeutic Drug Monitoring in Patients with Inflammatory Bowel Disease Receiving Stable Infliximab Maintenance Treatment

Abstract

Abstract Background Recent studies suggest that proactive therapeutic drug monitoring (TDM) in patients with inflammatory bowel disease (IBD) receiving infliximab (IFX) improves clinical outcomes. However, as proactive TDM may lead to increased medical costs, we aimed to determine the optimal interval for TDM during infliximab maintenance therapy in IBD patients. Methods We conducted a retrospective analysis of a prospective cohort comprising 103 patients with IBD on IFX maintenance therapy who went through proactive TDM between February 2020 and May 2023. Following dose optimization till achieving a therapeutic trough level (TL) of 3 to 10 ug/mL, we applied the Kaplan-Meier (KM) method to calculate the time to subtherapeutic IFX TL (two consecutive IFX TLs below 3 ug/mL). Results 90% of patients had a sustained therapeutic IFX TL for 10.3 months, whilst 80% had it for 14.3 months. In multivariable analysis, IFX TL at enrollment had a association with the risk of subtherapeutic IFX TL (P=0.025). Persistence rates for therapeutic IFX TL were significantly lower in patients with IFX TL from 3 to 5 µg/mL at recruitment than in those with IFX TL >5 µg/mL (P=0.017). For patients who had IFX TL between 3 to 5 µg/mL upon enrollment, the percentage of those who maintained therapeutic IFX TL was 80% after 12.0 months. The group with IFX TL greater than 5 µg/mL had a persistence rate of 90% after 12.3 months. Conclusion These results suggest that conducting annual measurement of IFX TL in patients with IBD who are on stable maintenance therapy with IFX, which may reduce the cost of proactive TDM.