It has been observed that COPD exacerbations are under-reported in China. One of the reasons for this is Chinese subjects with COPD cannot describe the symptoms of exacerbation mentioned in English. Hence this study aims to create a tool called CERT that will help Chinese physicians and subjects with COPD to recognize and report exacerbations. The study will be carried out in 4 stages: item identification, cognitive briefing, item reduction and creation of final CERTs. Two CERTs will be prepared, one for subjects with COPD and another for physicians. A total of approximately 200 subjects will be included in the study and each subject will contribute to only one step.