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Abstract: Poster Presentations |

RELATIVE SENSITIVITY AND LOWER LIMITS OF NORMAL FOR SPIROGRAPHIC MARKERS OF AIRWAY OBSTRUCTION FREE TO VIEW

James E. Hansen, MD*; Xing Guo Sun, MD; Karlman Wasserman, MD
Author and Funding Information

Harbor-UCLA Medical Center, Torrance, CA


Chest


Chest. 2005;128(4_MeetingAbstracts):391S. doi:10.1378/chest.128.4_MeetingAbstracts.391S
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Abstract

PURPOSE:  1) Develop mean and 95% confidence lower limit of normal (LLN) formulae for FEV3/FVC for Black, Latin, and White men and women to supplement the findings of Hankinson et al. 2) Ascertain comparative variability of FEV1/FVC, FEV3/FVC and FEF25-75 in never-smoking adults and evaluate their utility in measuring the effects of smoking on airway obstruction. 3) Develop and use the concept of 1-FEV3/FVC to identify airway obstruction.

METHODS:  We identified 5938 never-smokers and 3570 current smokers with spirometric data meeting American Thoracic Society standards from the NHANES-III nationwide database. In these groups we developed regression formulae for the FEV3/FVC, quantified variability and LLN of the FEV1/FVC, FEV3/FVC and FEF25-75 to identify abnormalities in current-smokers, and evaluated 1–FEV3/FVC as a marker of airflow obstruction.

RESULTS:  With normal aging, there were concurrent linear decreases in FEV1/FVC and FEV3/FVC and increases in 1-FEV3/FVC, the latter attributable to slower emptying of acini with longer time constants. By middle age these spirometric measurements worsened, on average, about 20 years earlier in current-smokers. Two-thirds of current-smokers who manifested airway obstruction had both FEV1/FVC and FEV3/FVC abnormal, while 1/6 had only FEV1/FVC abnormal and 1/6 had only FEV3/FVC abnormal. The normal variability of FEF25-75 is greatest and that of the FEV3/FVC is least. If <80% of mean predicted FEF25-75 values were used to identify abnormality, >25% of all never-smokers would have been falsely identified as abnormal. Using 95% confidence limits for FEF25-75, only 1% of never-smokers had isolated abnormal FEF25-75 while 42% of 683 smokers without restriction but with reduced FEV1/FVC and/or FEV3/FVC had normal FEF25-75 values (false negatives).

CONCLUSION:  FEV1/FVC, FEV3/FVC and 1-FEV3/FVC all characterize expiratory obstruction well. In contrast, FEF25-75 has an unacceptably large proportion of false negatives and false positives.

CLINICAL IMPLICATIONS:  Using <80% of mean predicted to define abnormality is statistically invalid. For valid spirographic assessment of airways obstruction, we recommend requiring statistically correct LLN and replacement of the FEF25-75 with the FEV1/FVC and FEV3/FVC.

DISCLOSURE:  James Hansen, None.

12:30 PM - 2:00 PM


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