Linking clinical variables with health-related quality of life. A conceptual model of patient outcomes

HEALTH-related quality of life (HRQL) is increasingly used as an outcome in clinical trials, effectiveness research, and research on quality of care. Factors that have facilitated this increased usage include the accumulating evidence that measures of HRQL are valid and "reliable,"¹the publication of several large clinical trials showing that these outcome measures are responsive to important clinical changes,^2-5and the successful development and testing of shorter instruments that are easier to understand and administer.^6-13Because these measures describe or characterize what the patient has experienced as the result of medical care, they are useful and important supplements to traditional physiological or biological measures of health status. Given this improved ability to assess patients' health status, how can physicians and health care systems intervene to improve HRQL? Implicit in the use of measures of HRQL in clinical trials and in effectiveness research is the concept that clinical