Cost-Effectiveness of Fecal Immunochemical Testing Alone vs Co-Testing With Helicobacter pylori Stool Antigen

Importance: Helicobacter pylori infection is the leading cause of gastric cancer, yet the economic value of population-based screening and eradication remains uncertain. Objective: To project the lifetime health benefits and costs of invitation to 1-time H pylori stool antigen testing added to biennial fecal immunochemical test (FIT) screening compared with FIT alone. Design, Setting, and Participants: Lifetime cost-effectiveness analysis conducted using a Markov decision-analytic model to simulate a cohort informed by a pragmatic randomized clinical trial in Changhua County, Taiwan. The model adopted a 30-year time horizon and projected long-term outcomes, including gastric and colorectal cancer mortality, quality-adjusted life-years (QALYs; incorporating both life expectancy and health-related quality of life), and health care expenditures. Costs were evaluated from a societal perspective. One-way and probabilistic sensitivity analyses were performed. Future costs and QALYs were discounted at an annual rate of 3%. Exposures: Helicobacter pylori stool antigen testing plus FIT or FIT alone. Main Outcomes and Measures: Incremental cost-effectiveness ratio of invitation for H pylori stool antigen testing plus FIT vs FIT alone, measured as the additional cost required to gain 1 QALY per person. Secondary outcomes included net monetary benefit and benefit-cost ratio. Results: Compared with FIT alone, invitation to co-testing was more effective and less expensive (dominant), with a base-case cost-saving incremental cost-effectiveness ratio of $2094 per QALY gained (95% CI, $12359 saved to $7291 additional cost). This resulted in a positive net monetary benefit, indicating that health benefits exceeded costs, and a benefit-cost ratio of 5.08, indicating an approximately 5-fold return on investment in the Taiwanese population. At a willingness-to-pay threshold of 1 × the Taiwan gross domestic product per QALY ($33365), invitation to co-testing remained cost-saving in 65.7% of simulations. From a US cost perspective, invitation to co-testing was not cost-saving but remained cost-effective at the trial base-case H pylori prevalence. Sensitivity analyses identified H pylori prevalence as the dominant driver; co-testing exceeded a $100000-per-QALY threshold when prevalence fell below 21.9%. Conclusions and Relevance: In a pragmatic real-world setting with incomplete adherence, invitation to combined H pylori stool antigen testing and FIT was more cost-effective than FIT alone, improving lifetime outcomes and yielding cost savings in Taiwan while remaining cost-effective in higher-cost settings under moderate H pylori prevalence.