Mean (95% CI) change in Clinical COPD Questionnaire (CCQ) with pulmonary rehabilitation, according to achievement (+) or non-achievement (−) of the established minimal clinically important difference (MCID) for the St George's Respiratory Questionnaire (SGRQ), Chronic Respiratory Questionnaire (CRQ) and COPD Assessment Test (CAT). Mean (95% CI) change in Clinical COPD Questionnaire (CCQ) with pulmonary rehabilitation, according to achievement (+) or non-achievement (−) of the established minimal clinically important difference (MCID) for the St George's Respiratory Questionnaire (SGRQ), Chronic Respiratory Questionnaire (CRQ) and COPD Assessment Test (CAT). The dotted line represents the proposed MCID of 0.4. Samantha S C Kon et al. Thorax 2014;69:793-798 Copyright © BMJ Publishing Group Ltd & British Thoracic Society. All rights reserved.