CCHE Seminar Series: Are the ‘Equal Value of Life Years Gained’ and ‘Health Years in Total’ Approaches Viable Alternatives to the QALY? Matters of Logic and Matters of Value
University of Alberta
Friday January 29th, 2020, 10am-12pm, Zoom
Abstract: Background: The US Institute for Clinical and Economic Review (ICER) reports cost per ‘life year’ (LY) and cost per ‘equal value of life year gained’ (evLYG), in addition to standard cost per quality-adjusted life year (QALY). The evLYG assigns identical value to similar life extensions, regardless of health-related quality-of-life (HRQoL). This is intended to prevent ‘discrimination’ against patients with poor HRQoL, but assigns no value to improvements in HRQoL during life extension. In addition, Basu and colleagues recently proposed the ‘Health Years in Total’ (HYT) approach, which claims to ‘overcome’ both the ‘discrimination’ against patients with poor HRQoL when using QALYs and the ‘undervaluing’ of improvements in HRQoL when using the evLYG. Our purpose is to consider the extent to which each approach satisfies (a) basic axioms of decision making, and (b) a set of properties potentially valued by decision makers. Methods: Using an illustrative example, we consider whether each approach satisfies (i) independence of irrelevant alternatives (IIA), and (ii) transitivity. We also consider whether dynamic inconsistencies arise over repeated comparisons. We then consider the extent to which each approach satisfies four potentially desirable properties: (i) assigns equal value to identical periods of life extension, regardless of HRQoL; (ii) assigns positive value to HRQoL improvements during life extension; (iii) assigns equal value to current life expectancies of identical length, regardless of HRQoL; and (iv) assigns positive value to HRQoL improvements during current life expectancy. Results: The HYT violates IIA, but satisfies transitivity provided that the “maximum survival under any given alternative” remains fixed across pairwise comparisons. The evLYG satisfies IIA and transitivity in a static comparison; however, a vicious circularity may result if comparisons are repeated following adoption of a new treatment. The QALY and LY satisfy IIA and transitivity in all cases. It is logically impossible to satisfy properties (i) and (ii), or properties (iii) and (iv), simultaneously; the HYT and QALY satisfy properties (ii) and (iv) only, the evLYG satisfies (i) and (ii) only, while the LY satisfies (i) and (iii) only. Conclusion: The HYT is not a viable alternative to the QALY since it violates IIA, while the evLYG is problematic due to dynamic inconsistencies. Since no measure can satisfy all potentially desirable properties, decision makers should determine which properties they value most and choose a logical approach consistent with these values.
Dr Mike Paulden is an Assistant Professor at the School of Public Health, University of Alberta. He is a health economist with an interest in methods for the economic evaluation of health technologies.
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