Health status, dyspnea, lung function and exercise capacity in patients with chronic obstructive pulmonary disease

SETTING: A secondary hospital outside Oslo. OBJECTIVE: To assess relationships between health status and measures of dy spnea, lung function and exercise capacity in patients with chronic obstruc tive pulmonary disease (COPD), to identify dimensions where lung-specific i nstruments associate and discriminate better than general measures. DESIGN: We assessed health status in 59 out-patients with COPD, using the f ollowing instruments: Short Form 36 (SF-36)-a general health status measure , Respiratory Quality of Life Questionnaire (RQLQ)-a lung-specific measure, the Karnofsky performance scale, and a rating scale. All patients rated th eir dyspnea and had spirometry and exercise capacity measured. RESULTS: Mean (SD) patient age was 57.3 (9.7) years, FEV1 47% (15%) of pred icted, 6 minute walk distance 503 m (122 m). Dyspnea was the strongest pred ictor for health status. Both SF-36 and RQLQ had dimensions associating wel l with dyspnea and exercise capacity The associations with FEV1 ranged from none to moderate. CONCLUSION: All RQLQ scales had a moderate to substantial association with indices of dyspnea and exercise capacity, while the SF36 associated well on ly in dimensions related to physical health. The general measure has a broa der scope and complements the lung-specific measure. These findings support the construct validity of both the SF-36 and the RQLQ, and justify using a general measure to supplement a lung-specific measure.