COPD classification methods and informativeness on mortality: contrasting evidences

Understanding whether the ABCD GOLD classification method is informative with respect to the spirometric classification of severity in predicting mortality of patients with chronic obstructive pulmonary disease (COPD) is subject of debate. The results of a study performed on a sample of the Norwegian population (HUNT2) were recently published. Such data showed the inferiority of ABCD classification in predicting mortality compared to the spirometric classification, which was considered the gold standard up to the 2011 version of GOLD guidelines. This result is not in line with the results of other studies that have shown the equivalence of the two classifications. The new GOLD classification seemed to be a step forward for what concerns understanding patient's needs, but it seems clear that the insertion of a single clinical variable to the spirometric data may not be exhaustive in describing all the phenomena related to a heterogeneous disease such as COPD. The publication of the HUNT study provides an opportunity to analyze how the evidence has been produced, which scientific speculations it offers, what considerations could be drawn and what further research would be appropriate.