title: Tests of the responsiveness of the COPD assessment test following acute exacerbation and pulmonary rehabilitation.
abstract: 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.
authors.affiliation: Division of Clinical Science, St. George's University of London, London, England. Electronic address: pjones@sgul.ac.uk.
authors.forename: Paul W
authors.initials: PW
authors.lastname: Jones
authors.affiliation: Center for Health Outcomes Research, United Biosource Corporation, Bethesda, MD.
authors.forename: Gale
authors.initials: G
authors.lastname: Harding
authors.affiliation: Center for Health Outcomes Research, United BioSource Corporation, London, England.
authors.forename: Ingela
authors.initials: I
authors.lastname: Wiklund
authors.affiliation: Global Health Outcomes, GlaxoSmithKline, London, England.
authors.forename: Pamela
authors.initials: P
authors.lastname: Berry
authors.affiliation: Global Health Outcomes, GlaxoSmithKline, London, England.
authors.forename: Maggie
authors.initials: M
authors.lastname: Tabberer
authors.affiliation: Center for Health Outcomes Research, United Biosource Corporation, Bethesda, MD.
authors.forename: Ren
authors.initials: R
authors.lastname: Yu
authors.affiliation: Center for Health Outcomes Research, United Biosource Corporation, Bethesda, MD.
authors.forename: Nancy K
authors.initials: NK
authors.lastname: Leidy
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D005541:Forced Expiratory Volume / Q000502:physiology; D006304:Health Status; D006801:Humans; D008297:Male; D008875:Middle Aged; D029424:Pulmonary Disease, Chronic Obstructive / Q000175:diagnosis / Q000503:physiopathology* / Q000534:rehabilitation*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index; D011795:Surveys and Questionnaires / Q000592:standards*