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 dyspnea, lung function and exercise capacity in patients with chronic obstructive pulmonary disease (COPD), to identify dimensions where lung-specific instruments associate and discriminate better than general measures.
DESIGN: We assessed health status in 59 out-patients with COPD, using the following 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 their dyspnea and had spirometry and exercise capacity measured.
RESULTS: Mean (SD) patient age was 57.3 (9.7) years, FEV1 47% (15%) of predicted, 6 minute walk distance 503 m (122 m). Dyspnea was the strongest predictor for health status. Both SF-36 and RQLQ had dimensions associating well 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 SF-36 associated well only in dimensions related to physical health. The general measure has a broader 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.