Burden of disease in both asthma and COPD: one questionnaire?

Abstract

<b>Introduction:</b> Overlap in clinical manifestations of asthma and COPD exist and distinction can be difficult. The asthma control questionnaire (ACQ) and clinical COPD questionnaire (CCQ) were developed to assess disease burden of respectively asthma or COPD. Our hypothesis is that one questionnaire could be developed to assess disease burden in both diseases. <b>Objective:</b> To develop a new questionnaire for disease burden in a cohort of patients with obstructive lung disease. <b>Methods:</b> In the outpatient clinic in the Franciscus Gasthuis in Rotterdam, data of patients with severe yet clinically stable asthma or COPD were prospectively collected (n=348). Patients completed the ACQ-5 and CCQ at the same day. Linear regression and Bland Altman were used to test correlation and agreement respectively. Factor analysis was used for item reduction and to develop one new questionnaire. <b>Results:</b> 252 patients with asthma and 96 with COPD were included. Correlation between ACQ and CCQ was in asthma (R2=0.677) and COPD (R2=0.688). Mean of the difference between ACQ and CCQ was 0.0637 with 95% confidence interval of -1.31 and 1.44. These limits of agreement of 1.4 points were larger than the minimal clinically important difference of the ACQ an CCQ (0.5). There was no fixed or proportional bias. Factor analysis determined a new 9-item questionnaire by combining ACQ1, ACQ2, ACQ4, ACQ5, CCQ1, CCQ3, CCQ6, CCQ7 and CCQ10. <b>Conclusion:</b> The ACQ and CCQ are correlated but are not interchangeable, because the limits of agreement are not clinically acceptable. A new questionnaire could be developed for obstructive lung disease by combining nine questions of the ACQ and CCQ: further validation in a prospective cohort is warranted.