False positive rates of multiple pulmonary function tests in healthy subjects.

Spirometry, diffusing capacity and lung volume tests were performed on 251 healthy, nonsmoking volunteers in order to determine the rate of false positive results of multiple pulmonary function tests. Each test had an approximately 5% false positive rate, defined here as the percentage of normal subjects classified as abnormal by the tests. The percentage of subjects with at least one abnormal test rose substantially as the number of tests performed increased. When simple spirometry (FVC, FEV1, FEV1/FVC) was performed, 10% had at least one abnormal test; this rose to 24% when a complete battery of 14 tests was performed.