Measuring functional status in chronic lung disease: conclusions from a randomized control trial.

The optimal method of assessing the effect of treatment on the day-to-day function of patients with chronic airflow limitation has not yet been established. Therefore, we examined the performance of the 6-min walk test, a rating of dyspnea following the walk test, and three different questionnaires measuring dyspnea in daily activities, in a controlled trial of inhaled salbutamol and oral theophylline in 24 patients with primary fixed chronic airflow limitation. Clinically important and statistically significant effects of salbutamol and theophylline on dyspnea during the day-to-day activities were detected by each measure, but the Chronic Respiratory Questionnaire (CRQ) was more powerful than the other questionnaires, either the Oxygen Cost Diagram or the Medical Research Council Dyspnea Questionnaire as modified by the Rand Corporation. Changes in the CRQ dyspnea score showed a higher correlation with changes in spirometry, walk test score, dyspnea following the walk test, and global ratings of dyspnea than did the other two measures. We conclude that the CRQ is a responsive, valid measure of functional status for clinical trials in chronic lung disease.