From Quality-Adjusted Life Years (QALY) to Equal Value of Life Years (evLY): A Study on Non-Alcoholic Steatohepatitis (NASH) Subpopulations

OBJECTIVES: The evLY, a measure developed by ICER US, can be an alternative to QALY in cost-effectiveness analyses (CEA). It involves applying healthy population utility for the life years gained thanks to the intervention. The underlying idea is to avoid discriminating patients with a lower baseline utility level. This study aims to calculate both evLY and QALY in a model for NASH considering two different subpopulations and examine the impact of using evLY instead of QALY on results.

METHODS: The cohort Markov model estimated the cost-effectiveness of a hypothetical curative therapy for NASH, compared separately to standard of care (SoC) and a biologic therapy. The evLY formula, following ICER US methodology, was applied in this model: the standard QALY approach was used for LYs shared by both the intervention and the comparator, while a utility value of a healthy life year was considered for LY gained with the intervention, (assumed to be 0.851, based on the utility of a healthy US population). Two NASH subpopulations were considered: patients with super obesity, and patients without obesity. Except for the utility levels, all the inputs were identical in the 2 subpopulations.

RESULTS: Baseline utility was calculated as 0.643 for super obese patients and 0.786 for those without obesity. The QALY-based ICER of the curative therapy vs SoC was 22% higher for super obese patients compared to those without obesity. Using evLY significantly reduced this difference to only 2%.

CONCLUSIONS: This example illustrates how the evLY approach mitigates discrimination against patients with lower baseline quality of life. The quantity of evLY varies with the reference comparator, unlike the number of QALY which is independent from the reference treatment.