The authors comment on research which examined the accuracy of the ratio thresholds of forced expiratory volume in the first second to forced vital capacity (FEV1:FVC) for define chronic obstructive pulmonary disease (COPD). Topics covered are the basis for discriminative accuracy, C statistic values that denote poor predictive capacity and association of COPD-related hospitalization and mortality with cardiovascular disease, pneumonia and nonrespiratory causes.