Therapeutic Drug Monitoring in Patients with Ulcerative Colitis on Infliximab: A Cost-Effectiveness Analysis

Background and aims: Ulcerative colitis (UC) can be treated with infliximab (IFX). Therapeutic drug monitoring (TDM) can yield superior outcomes, but its cost-effectiveness is unknown.

Methods: We used a decision analytic Markov model to conduct a cost-effectiveness analysis comparing proactive TDM, reactive TDM, no TDM, and combinations of proactive and reactive TDM in 25-year-old patients with UC started on IFX. Under proactive TDM, IFX concentration and anti-drug antibodies were measured every 6 months and during a flare; under reactive TDM, these were only measured during a flare. Patients with flares experienced decreased quality of life (QoL) and risked further complications. We evaluated lifetime costs (2021 U.S. dollars), quality-adjusted life years (QALYs), and incremental cost-effectiveness ratios, all discounted at 3% annually, from a healthcare sector perspective. We performed probabilistic sensitivity analysis (PSA) and deterministic sensitivity analyses. We used a willingness-to-pay threshold of $100,000 per QALY gained.

Results: All TDM strategies increased QALYs and healthcare costs. Compared to no TDM, reactive TDM increased costs from $496,700 to $497,500 ($3,200 per QALY gained). 1 year of proactive TDM followed by reactive TDM increased costs to $508,600 ($63,800 per QALY gained relative to reactive TDM). In 46% of PSA samples, 1 year of proactive TDM followed by reactive TDM was most likely to be the optimal strategy. This strategy was less likely to be cost-effective when remission QoL was lower and when post-surgical QoL was higher.

Conclusion: 1 year of proactive TDM followed by reactive TDM is cost-effective in patients with UC on IFX.