GOLD Classification of COPD: Discordance in Criteria for Symptoms and Exacerbation Risk Assessment

The new A-B-C-D Global Initiative for Chronic Obstructive Lung Disease (GOLD) classification of severity of chronic obstructive pulmonary disease (COPD) is based on combined symptoms and exacerbation risk assessment. The assumed equivalence between dyspnoea modified Medical Research Council (mMRC) grade >= 2 and COPD Assessment Test (CAT) score >= 10 to identify more symptoms has been questioned. Whether the exacerbation risk assessment criteria, old GOLD spirometry staging and frequency of exacerbations, are equivalent has not been examined. We evaluated the extent of agreement between these alternative criteria and whether it improved by redefining the equivalence between mMRC grade and CAT score. CAT scores, mMRC grades of dyspnoea, frequency of exacerbations and spirometry stages were computed in 400 patients with COPD. Receiver operating characteristic curve was analysed to determine the best CAT score to identify more symptoms. CAT scores across mMRC grades and the frequency of exacerbations across spirometry stages showed substantial overlaps. The symptoms criteria gave discordant classification in 88 (22%) patients (kappa 0.62) and the exacerbation risk assessment criteria in 181 (45%) patients (kappa 0.12). A CAT score of >= 10 had 82% sensitivity but 24% specificity to identify mMRC grade >= 2, while a score of 17 had 98% specificity but a low sensitivity of 52% and did not improve the agreement. We conclude that symptoms and exacerbation risk assessment criteria of the new GOLD classification yield discordant group categorisations. Lack of any satisfactory equivalence between CAT score and mMRC grades implies that the former cannot be used alone. Using the higher of mMRC >= 2 and CAT score >= 17 to identify more symptoms would avoid discordant categorisation.