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.