Health related utility measurement: an introduction.

Utility measures of health related quality of life are preference values that patients attach to their overall health status. In clinical trials, utility measures summarize both positive and negative effects of an intervention into one value between 0 (equal to death) and 1 (equal to perfect health). These measures allow for comparison of patient outcomes of different diseases, and for comparison between various health care interventions. There are 2 different approaches to utility measurement. The first is to classify patients into categories based on their responses to questions about their functional status, as for instance the Quality of Well-Being Questionnaire and the European Quality of Life Measure (EUROQOL). The 2nd approach is to ask patients to assign a single rating to their overall health by means of rating scale, standard gamble, time tradeoff, or willingness to pay. The Quality Adjusted Life Year (QALY) outcome measure includes both effects in terms of quality of quantity of life. Utilities are used as weights to adjust life years for the quality of life in order to calculate QALY. Both QALY and utilities are useful in decision making regarding appropriate procedures for groups of patients.