Chest
Volume 129, Issue 2, February 2006, Pages 369-377
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Original Research
Discriminating Measures and Normal Values for Expiratory Obstruction

https://doi.org/10.1378/chest.129.2.369Get rights and content

Objectives

To 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 (FEF25–75) 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.

Design

Analysis of the Third National Health and Nutrition Examination Survey (NHANES III) database of never-smokers and current smokers.

Participants

A 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 results

After 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 FEF25–75 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 FEF25–75.

Conclusions

FEV1/FVC, FEV3/FVC, and 1 − FEV3/FVC characterize expiratory obstruction well. In contrast, FEF25–75 measurements can be misleading and can cause an unacceptably large number of probable false-negative results and probable false-positive results.

Section snippets

Subjects

Data from NHANES III24 were extracted for men and women ≥ 20 years of age for the following ethnic-racial groups: white (white); African-American (black); and Mexican-American (Latin or Latina). These data, from unidentified subjects, had been ethically obtained with Institutional Review Board approval. The term never-smokers included individuals those who had not smoked pipes, cigars, or > 100 cigarettes in a lifetime, and excluded those with known respiratory, skeletal, or neurologic

Results

Several key spirometric values, with respect to ethnicity, gender, age, and height, are provided for the NHANES III never-smokers and current smokers in Table 1. The number of never-smokers (5,938) differs from that of Hankinson et al25 because of differences in age ranges and screening procedures. Table 2 gives the factors needed to derive the linear regression equations for FEV1/FVC and FEV3/FVC for never-smokers (eg, FEV1/FVC or FEV3/FVC = mean constant − age constant × age). The mean

Discussion

This study introduces the concept of the 1 − FEV3/FVC fraction and gives data confirming the utility of the FEV3/FVC ratio in assessing expiratory airway obstruction We took advantage of the NHANES III-verified spirometric and demographic data that were available from a large and diverse US population, and expand on the prior excellent analyses of Hankinson et al25 by adding normal reference values for FEV3/FVC in white, black, and Latin men and women, 20 to 80 years of age (Table 2). We

ACKNOWLEDGMENT

We thank the planners, surveyors, technicians, and subjects who participated in the NHANES III, and the manuscript reviewers for their suggestions.

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    Reproduction of this article is prohibited without written permission from the American College of Chest Physicians (www.chestjournal.org/misc/reprints.shtml).

    This research was supported by the Los Angeles Biomedical Institute at Harbor-UCLA Medical Center.

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