Measuring quality of life: methodological issues.

Quality of life is a term used in a number of disciplines, and definitions and conceptualizations vary from utility of health states to life satisfaction and from possession of socially desirable characteristics to positive affect. This article offers a taxonomy of measures of quality of life based on measurement characteristics, which are shown to closely parallel definitions and their underlying assumptions. The fact that basic philosophical issues and ethical assumptions underlie quality of life measurement is stressed. Clinimetric characteristics of quality of life measures (validity, reliability, responsiveness, sensitivity, practicality, face validity, interpretability) are reviewed. This article concludes with a discussion of a number of additional methodological issues, including the following: measurement of change in the quality of life; generic v disease-specific measures; the use of self-reports by persons with mental health or cognitive-communicative problems; and the use of proxy reporters of quality of life.