Tests of the responsiveness of the COPD assessment test following acute exacerbation and pulmonary rehabilitation.

BACKGROUND The COPD Assessment Test (CAT) is an eight-item questionnaire suitable for routine clinical use that shows reliability and validity in stable and exacerbating COPD. METHODS Study 1 assessed CAT responsiveness to changes in health status in 67 patients during an exacerbation (days 1-14). Study 2 assessed CAT responsiveness in 64 patients undergoing pulmonary rehabilitation (days 1-42). Correlations between CAT and other outcome measures were examined. RESULTS In study 1, mean 14-day improvement in CAT score was -1.4 ± 5.3 units (P = .03). In patients judged to be responders (clinician defined) change in score was -2.6 ± 4.4; in nonresponders it was -0.2 ± 5.9. In study 2, the mean improvement in CAT score was -2.2 ± 5.3 (P = .002); the effect size for the change was -0.33. Effect size for changes in the Chronic Respiratory Questionnaire-Self Administered Standardized (CRQ-SAS) form domain scores ranged from -0.02 to 0.34. Change in 6-min walk distance (6MWD) was 41 ± 55 m. CAT and CRQ-SAS domain scores correlated at baseline (r = -0.54 to -0.69, P < .0001) and in terms of change following pulmonary rehabilitation (r = -0.39 to -0.63, P < .01). Correlations were less strong between change in the CAT and St. George Respiratory Questionnaire for COPD in study 1 (r < 0.24) and for 6MWD (r < 0.11) in study 2. CONCLUSIONS These studies indicate that the CAT is sensitive to changes in health status following exacerbations and is as responsive to pulmonary rehabilitation as more complex COPD health status measures.

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