The chronic obstructive pulmonary disease (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 units ± 5.3 (p = 0.03). In patients judged to be responders (clinician-defined) change in score was -2.6 ± 4.4; in non-responders it was -0.2 ± 5.9. In Study 2, the mean improvement in CAT score was -2.2 ± 5.3 (p = 0.002); the effect size for the change was -0.33. Effect size for changes in the Chronic Respiratory Questionnaire - Self Administered Standardized form (CRQ-SAS) domain scores ranged from -0.02 to 0.34. Change in 6-minute walk distance was 41 ± 55 m. CAT and CRQ-SAS domain scores correlated at baseline (r = -0.54 to -0.69, p < 0.0001) and in terms of change following pulmonary rehabilitation (r = -0.39 to -0.63, p < 0.01). Correlations were less strong between change in the CAT and SGRQ in Study 1 (r<0.24), and for 6-minute walk distance (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.