Selecting among health-related quality-of-life instruments.

A method of evaluating health-related quality-of-life (HRQL) instruments is described. Selection of an HRQL instrument should be based on the intended purpose and how well the instrument satisfies that purpose. An available methodological framework for developing HRQL instruments can be used; its premise is that the developmental process and psychometric properties of an instrument vary with the intended purpose. Intended purposes are classified as evaluative, discriminative, and predictive. Developmental steps are selection of items, item scaling, item reduction and assessment of internal consistency, and determination of reliability, validity, and responsiveness. Specific criteria apply to each step. An evaluation of asthma-specific HRQL instruments demonstrates use of the method. A useful method exists for selecting among available HRQL instruments on the basis of the instruments' intended purposes.