OBJECTIVES: Therapeutic Drug Monitoring (TDM), to measure drug and anti-drug antibodies and guide therapeutic adjustments, has been associated with positive clinical outcomes when using biologics such as infliximab (IFX) to treat inflammatory bowel disease (IBD). TDM may be ordered reactively or proactively as the preferred standard of care versus empiric dosing. This study aims to estimate the 2021 incremental budgetary change in per member per year (PMPY) in the US when a proactive TDM approach is implemented for IBD patients treated with IFX.

METHODS: Through a probabilistic simulation model over a 2-year period, we compared proactive TDM, reactive TDM, and empiric scenarios in a simulated cohort of 161,781 US patients on IFX treatment for 2021 (Clarivate/DRG, 2021). With proactive TDM, testing occurred as part of a routine monitoring strategy (2x per year). In reactive scenarios, testing was prompted by a clinical recurrence of disease. No TDM occurred in the empiric scenario. We based this study on published literature and clinician interviews. Costs of health care resource utilization (HCRU), TDM, and drugs were obtained from literature and adjusted to 2021 values.

RESULTS: Results suggest proactive TDM strategies in the US may be associated with one-year savings average of $5,520 and $9,229 PMPY when compared to reactive and empiric, respectively. Proactive TDM had higher IFX and testing costs compared to reactive, but lower HCRU (IBD-related hospitalizations, procedures, visits). Compared to empiric, proactive TDM had higher testing costs, lower IFX costs, and significantly lower HCRU.

CONCLUSIONS: A proactive TDM strategy is associated with total cost-of-care savings resulting from lower IBD-related HCRUs, which are expected from suboptimal dosing and subsequent disease complications. This budget impact analysis highlights the cost value of efficiently maintaining optimal IFX dosing and avoiding drug waste by prescribing the right dose for the right patient.