Quality of life: an overview of the concept and measures.

This paper summarizes the concepts and measures of quality of life. Although numerous attempts have been made to conceptualize and operationalize quality of life, there has been no universally accepted standard for the study design, data collection and data analysis of studies that use quality of life as an outcome measure. Quality of life has been defined either as a measure of happiness and satisfaction with life, or goal achievement, or social utility. However, most studies conceptualize and measure quality of life as a composite that consists of several domains. There are two approaches to the measurement of quality of life, namely, the psychometric approach and the utility approach. A quality of life measure can be either generic or disease-specific. High reliability and validity are important criteria for a credible quality of life instrument. Published clinical studies which use quality of life as an outcome measure have to be assessed on the basis of the appropriateness of the study design, the validity of study results and the applicability of the quality of life measure to the specific patient group.