Minimally important difference in health gain valuation

BACKGROUND: Minimal important difference (MID) thresholds distinguish noticeable from meaningful health gains, yet reimbursement decisions often fund high-cost therapies with marginal benefit. Clarifying meaningful patient-reported improvement is important for interpreting evidence and allocating resources. RESEARCH DESIGN AND METHODS: We reviewed how MID concepts are defined and used across outcomes research, clinical trials and health technology assessment (HTA), and estimated Croatia's first EuroQol Visual Analogue Scale (EQ-VAS) MID in a representative sample (n = 401), examining whether thresholds vary by baseline health and a €100/month co-payment. Respondents stated the smallest noticeable and meaningful EQ-VAS improvement for a free intervention and the same intervention requiring a co-payment for one year. Analyses combined descriptive statistics, rank-based tests and multivariable regression. RESULTS: Mean MID was 7.9 EQ-VAS points when treatment was free and increased to 8.7 with co-payment, with higher thresholds among those with poorer baseline health. The co-payment scenario is interpreted cautiously as reflecting a worthwhile-improvement threshold rather than a pure intrinsic MID. CONCLUSIONS: Elicited thresholds were context-sensitive; however, the co-payment scenario captures what respondents considered worth paying for, arguing against universal MID cutoffs. In HTA, MIDs should serve as patient-centered interpretive benchmarks complementing cost-effectiveness evidence and considerations such as equity and societal preferences.