• James E Hansen, Xing-Guo Sun, and Karlman Wasserman.
• Division of Respiratory and Critical Care Physiology and Medicine, Department of Medicine, Harbor-UCLA Medical Center, Los Angeles Biomedical Institute at Harbor UCLA Medical Center, Torrance, CA. Electronic address: jhansen@labiomed.org.
• Chest. 2006 Feb 1; 129 (2): 369-377.

ObjectivesTo develop mean and 95% confidence limits for the lower limit of normal (LLN) values for forced expiratory volume in 3 s (FEV3)/FVC ratio for Latin, black, and white adults; to ascertain comparative variability of the FEV1/FVC ratio, the FEV3/FVC ratio, and forced expiratory flow, midexpiratory phase (FEF(25-75)) in never-smoking adults; to evaluate their utility in measuring the effect of smoking on airflow limitation; and to develop and use the fraction of the FVC that had not been expired during the first 3 s of the FVC (1 - FEV3/FVC) to identify the growing fraction of long-time-constant lung units.DesignAnalysis of the Third National Health and Nutrition Examination Survey (NHANES III) database of never-smokers and current smokers.ParticipantsA total of 5,938 adult never-smokers and 3,570 current smokers from NHANES III with spirometric data meeting American Thoracic Society standards.Measurements And ResultsAfter establishing new databases for never-smokers and current smokers, we quantified the mean and LLN values of FEV3/FVC in never-smokers, and identified spirometric abnormalities in current smokers. When associated with older age, FEV3/FVC decreases and 1 - FEV3/FVC increases as FEV1/FVC decreases. On average, using these measurements, the condition of current smokers worsened about 20 years faster than that of never-smokers by middle age. If < 80% of the mean predicted FEF(25-75) was used to identify abnormality, over one quarter of all never-smokers would have been falsely identified as being abnormal. Using 95% confidence limits, 42% of 683 smokers with reduced FEV1/FVC and/or FEV3/FVC would have been judged as normal by FEF(25-75).ConclusionsFEV1/FVC, FEV3/FVC, and 1 - FEV3/FVC characterize expiratory obstruction well. In contrast, FEF(25-75) measurements can be misleading and can cause an unacceptably large number of probable false-negative results and probable false-positive results.

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