Brazilian version of the Clinical COPD Questionnaire, administered by interview: reliability and validity measurement properties

Objective: To test the reliability, validity, and interpretability of the Brazilian version of the Clinical COPD Questionnaire (CCQ) in patients with COPD. Methods: Fifty patients with COPD completed the CCQ by interview on two occasions. At the first visit, the CCQ was administered twice, by two different raters, approximately 10 min apart; the patients also underwent spirometry and were administered the COPD Assessment Test, the modified Medical Research Council scale, and Saint George's Respiratory Questionnaire (SGRQ). At the second visit (1-2 weeks later), the CCQ was readministered. We tested the hypothesis that the CCQ total score would correlate positively with the total and domain SGRQ scores (r >= 0.5). Results: Of the 50 patients, 30 (60%) were male. The mean age was 66 +/- 8 years, and the mean FEV1 was 4 4.7 +/- 17.9% of the predicted value. For all CCQ items, Cronbach's alpha coefficient (95% CI) was 0.93 (0.91-0.96). To analyze the interrater reliability and test-retest reliability of the CCQ, we calculated the two-way mixed effects model/single measure type intraclass correlation coefficient (0.97 [95% CI: 0.95-0.98] and 0.92 [95% CI: 0.86-0.95], respectively); the agreement standard error of measurement (0.65 for both); the smallest detectable change at the individual level (1.81 and 1.80, respectively) and group level (0.26 and 0.25, respectively); and the limits of agreement (-0.58 to 0.82 and -1.14 to 1.33, respectively). The CCQ total score correlated positively with all SGRQ scores (r >= 0.70 for all). Conclusions: The Brazilian version of the CCQ showed an indeterminate measurement error, as well as satisfactory interrater/test-retest reliability and construct validity.