Quality-adjusted life years: how useful in medico economic studies.

Cost-effectiveness analysis has evolved as a practical response to the need to allocate limited resources for health care. It can be used to compare interventions whose effects on health are different if the measure of effectiveness captures all the important health dimensions of the effects of the interventions. Using the quality-adjusted life year (QALY) as the unit of effectiveness attempts to approach this ideal and is currently the approach recommended by many consensus groups. Conventional QALYs represent time spend in a series of "quality-weighted" health states, where the quality weights reflect the desirability of living in the state. Many challenges arise when preferences are incorporated into an economic analysis. The purpose of this paper is to highlight some of the issues surrounding the use of QALYs and to encourage researchers to present their methodology in a clear and transparent way.