Background: Both the COPD Assessment Test (CAT) and the Clinical COPD Questionnaire (CCQ) were recommended as comprehensive symptom measures by the Global Initiative for Chronic Obstructive Lung disease. The main objective of this work was to compare the evalua­tion of symptom severity with the CAT and the CCQ and find a cutoff value of the CCQ for the Chinese clinical population.
Methods: Patients diagnosed with stable COPD in the outpatient department who completed the CAT and CCQ were enrolled from November 2015 to December 2016. Scores of 0–10, 11–20, 21–30, and 31–40 represent low, medium, high, and very high impact level, respectively, by CAT. Scores of the CCQ can be considered as acceptable (CCQ<1), acceptable for moderate disease (1≤CCQ<2), instable-severe limited (2≤CCQ<3), and very instable-very severe limited (CCQ≥3).
Results: According to the CAT, only 20.4% of patients belonged to the high (21≤CAT≤30) and very high (31≤CAT≤40) impact levels, which were statistically lower than those of the CCQ, which classified over half of the population (51.1%) into the instable-severe limited (2≤CCQ<3) and very instable-very severe limited (CCQ≥3) categories (P <0.001). The kappa of agreement for the symptom groups by CAT and CCQ (cutoff point 1.5) was 0.495, but only slight agreement (0.144) was found between the CAT and CCQ with the cutoff point of 1.0. The CAT and the total CCQ had a strong correlation (rho=0.776, P <0.01). The CCQ 1.0 and 1.5 corresponded to CAT 4.2 and 9.7, respectively. The CAT 10.0 was equivalent to 1.53 of the CCQ. In addition, with higher scores of the CAT and CCQ, subjects displayed more impairment in lung function, higher levels on modified Medical Research Council, and higher exacerbation rates in the last year (P <0.001). Similarly, patients with more exacerbations presented worse scores on the CAT and total CCQ as well as its 3 domains (P <0.001).
Conclusion: Compared with the CAT, the CCQ was more likely to classify the patients into more severe categories, and 1.5 might be a better cutoff point for the CCQ than 1.0. Both the CAT and the overall CCQ with its 3 domains were able to discriminate between groups of patients that differ in COPD severity.
Keywords: chronic obstructive pulmonary disease, COPD, the Clinical COPD Questionnaire, CCQ, the COPD Assessment Test, CAT