Generic and specific measurement of health-related quality of life in a clinical trial of respiratory rehabilitation

The purpose of this study was to compare the performance of measures of hea lth-related quality of life in a randomized controlled trial of respiratory rehabilitation versus conventional community care for patients with chroni c airflow limitation. The study included 89 stable patients with moderate t o severe chronic airflow limitation with measurement of health status at 12 , 18, and 24 weeks. Outcomes included two disease-specific (the Oxygen Cost Diagram and the Chronic Respiratory Questionnaire [CRQ]) measures, a gener ic health profile (the Sickness Impact Profile [SIP]), and two utility meas ures (the Standard Gamble and the Quality of Well-Being index [QWB]). Of th e measures, only the four domains of the CRQ (dyspnea, fatigue, mastery, an d emotional function) showed statistically significant differences (P less than or equal to 0.05) between treatment and control groups. Correlation be tween change in the CRQ and change in other relevant measures, including th e 6-minute walk test and global ratings of change in dyspnea, fatigue, and emotional function were generally weak to moderate (from 0.19 to 0.51). All correlations between change in the QWB, SIP, and Standard Gamble and other measures were very weak or weak (up to 0.30). Correlation between change i n the three generic measures were all very weak (<0.15). The results sugges t that unless investigators include responsive and valid disease-specific m easures of health-related quality of life in controlled trials in chronic d iseases, they risk misleading conclusions about the effect of treatments on health status. J CLIN EPIDEMIOL 52;3:187-192, 1999. (C) Elsevier Science I nc.