Background The global strategy for the diagnosis,management and prevention of chronic obstructive pulmonary disease (COPD) guidelines classify patients into four groups according to the number of symptoms and the level of future risk of acute exacerbation COPD (AECOPD).This study aimed to compare the results of different methods used in diagnosis of COPD and evaluate the accuracy of the assessment methods in guiding clinical practice.Methods A survey was conducted of 194 COPD outpatients between March and September 2012.Demographic characteristics,the number of exacerbations the patient has had within the previous 12 months,COPD assessment test (CAT),Modified British Medical Research Council (mMRC) scale,and results of the lung function tests were recorded.Results Of the 194 patients assessed,21 had a CAT score ≥10 and an mMRC grade ≤1,13 had a CAT score ＜10 and an mMRC grade ≥2.A predicted forced expiratory volume in one second (FEV1％) of ＜50％ with less than two acute exacerbations was observed in 39 patients,while a predicted FEV1％ of ≥50％ was noted in 20 patients with two or more acute exacerbations.The sensitivity of a predicted FEV1％ ＜50％ in predicting the risk of AECOPD in the future was 80.9％,while that in the real number of AECOPD events recorded was 62.8％,the difference being statistically significant (P=0.004).The sensitivity of CAT in predicting the severity of symptoms was 90％,while that of mMRC was 83.8％,and the difference was not statistically significant.Conclusions The COPD assessment method recommended by the global initiative for chronic obstructive pulmonary disease (GOLD) 2011 is complicated and should be simplified.CAT is more comprehensive and accurate than mMRC.The lung function classification is a better tool for predicting the risk of AECOPD in the future,and the number of AECOPD can be referred to when required.