What defines abnormal lung function?

A major concern with the GOLD criteria for defining chronic obstructive pulmonary disease (COPD) is that the use of 70% as a fixed cut-off for forced expiratory volume in 1 s (FEV1) will add a significant number of false positives compared with the use of a true lower limit of normal.1 2 The recent paper in Thorax by Mannino et al 3 argues that this false positive rate is acceptable because they found that these false positive subjects had an increased hazard of death when compared with those …