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Using dynamics of forced expiration to identify COPD where conventional criteria for the FEV1/FVC ratio do not match

The definition of chronic obstructive pulmonary disease (COPD) based on a fixed forced expiratory volume in 1 s (FEV1)/forced vital capacity (FVC) ratio or on the lower limits of FEV1/FVC of a healthy reference population is the subject of continuous debate. We explored whether dynamics of forced expiratory flow decline on spirometry can identify subjects with and without COPD when the two key diagnostic criteria are discordant.