Quality-Adjusted Life Years

The quality-adjusted life year, or QALY, is the standard outcome measure of cost-utility analysis in health economics. It combines length and quality of life into one number by weighting each year a person lives by a utility value reflecting their health-related quality of life during that year, on a scale where one is full health and zero is death. One year in perfect health is one QALY; two years lived at a utility of one half is also one QALY. Because the metric expresses survival and health-related quality of life in a single unit, it lets analysts compare interventions that extend life, improve quality of life, or do both, and it forms the denominator of the incremental cost-effectiveness ratios that health-technology agencies use to decide what to fund. George Torrance set out the methods for measuring the health-state utilities at the heart of the QALY, and Weinstein, Torrance, and McGuire later distilled the concept and its construction for a broad audience.