Fixed ratio or lower limit of normal as cut-off value for FEV1/VC: An outcome study.
There is no consensus on the appropriate cut-off level for the ratio between forced expiratory volume and vital capacity (FEV1/VC) for the diagnosis of chronic obstructive pulmonary disease (COPD). Application of a fixed ratio of 0.7 carries the risk of false positive diagnoses in elderly subjects and false negative diagnoses in younger subjects. The use of the lower limit of normal (LLN) of an in