Quality-adjusted life years.

Many health systems now use cost-effectiveness analysis to decide which interventions and programmes to fund. A key issue for such decision making is how to measure health outcomes from interventions to reflect changes in both health-related quality of life and life expectancy. For some decision makers, including the National Institute for Health and Clinical Excellence in the UK, the quality-adjusted life-year (QALY) is central to health measurement. This article describes the concept of the QALY, its derivation, and its strengths and weaknesses.