COPD Assessment Test in Bronchiectasis: Minimum Clinically Important Difference and Psychometric Validation: A Prospective Study.

BACKGROUND: Health-related quality of life (QoL) is one of the most important end points in bronchiectasis (BE). However, the majority of health-related QoL questionnaires are time-consuming or not validated in BE. The COPD Assessment Test (CAT) is an easy-to-use questionnaire. The objective of this study was to perform a complete validation of the CAT in BE.

METHODS: This was an observational, multicenter, prospective study in patients with BE. Psychometric properties of the CAT were measured: internal consistency (Cronbach α), repeatability (test-retest; intraclass correlation coefficient), discriminant validity (correlation with severity scores), convergent validity (correlation with some validated QoL questionnaire and other clinical variables of interest), longitudinal validity (measuring before and after each exacerbation during follow-up to determine the sensitivity to change and responsiveness), predictive validity to future exacerbations, and finally minimum clinically important difference.

RESULTS: Ninety-six patients were included and followed up for 1 year. Their mean age was 62.2 (15.6) years (79.2% women). The CAT showed excellent internal consistency (α, 0.95) and repeatability (intraclass correlation coefficient, 0.95). The validity of the CAT was excellent in all the measures (almost all with a Pearson coefficient > 0.40) except for the correlations with severity scores (Pearson coefficient between 0.22 and 0.26). Sensitivity to change before and after exacerbations was set at between 5.4 and 5.8 points. A CAT value ≥ 10 points showed prognostic value for patients with more than one exacerbation, and finally the minimum clinically important difference was set at 3 points.

CONCLUSIONS: The CAT presented excellent psychometric properties and is a questionnaire that is easy to use and interpret in patients with BE.