Properties of the COPD assessment test in a cross-sectional European study

Abstract

A short, easy-to-use health status questionnaire is needed in the multidimensional assessment of chronic obstructive pulmonary disease (COPD) in routine practice. The performance of the eight-item COPD assessment test (CAT) was analysed in 1,817 patients from primary care in seven European countries. The CAT has a scoring range of 0-40 (high score representing poor health status). Mean CAT scores indicated significant health status impairment that was related to severity of airway obstruction, but within each Global Initiative for Obstructive Lung Disease stage (I to IV) there was a wide range of scores (I: 16.2 ± 8.8; II: 16.3 ± 7.9; III: 19.3 ± 8.2; and IV: 22.3 ± 8.7; I versus II, p = 0.88; II versus III, p<0.0001; III versus IV, p = 0.0001). CAT scores showed relatively little variability across countries (within ± 12% of the mean across all countries). Scores were significantly better in patients who were stable (17.2 ± 8.3) versus those suffering an exacerbation (21.3 ± 8.4) (p<0.0001); and in patients with no (17.3 ± 8.1) or one or two (16.6 ± 8.2) versus three or more (19.7 ± 8.5) comorbidities (p<0.0001 for both). The CAT distinguished between classes of other impairment measures and was strongly correlated with the St George's Respiratory Questionnaire (r = 0.8, p<0.0001). The CAT is a simple and easy-to-use questionnaire that distinguishes between patients of different degrees of COPD severity and appears to behave the same way across countries.