Ethnic- and sex-free formulae for detection of airway obstruction.
BACKGROUND
Spirometric detection of airway obstruction in adults requires separate predictive formulae for each ethnicity and sex for percentage of FEV(1)/FVC (%FEV(1)/FVC) and percentage of FEV(3)/FVC (%FEV(3)/FVC), the major measurements for defining airway obstruction.


OBJECTIVE
To eliminate the need for multiple formulae for black, Latin, and white men and women by developing single formulae with less variance than current formulae for %FEV(1)/FVC and %FEV(3)/FVC.


METHODS
Data from nearly 6,000 healthy never-smokers 20.0-79.9 yr of age in the Third National Health and Nutrition Examination Survey were reevaluated mathematically and graphically based on the preliminary hypothesis that predictive normal FEV(1)/FVC and FEV(3)/FVC ratios could be calculated from the age and FVC alone, without considering ethnicity, sex, or height. Current and new formulae were evaluated, first considering the population as consisting of 36 equally weighted subgroups (6 decades x 3 ethnicities x 2 sexes) and then weighting each individual equally.


RESULTS
For each year of age, the slope of %FEV(1)/FVC versus FVC approximated -1.8%/l/yr; the slope of %FEV(3)/FVC versus FVC approximated -0.8%/l/yr. After trial and error iterations, the optimal formulae were %FEV(1)/FVC = 98.8 - 0.25 x years - 1.79 x FVC and %FEV(3)/FVC = 105.4 - 0.20 x years - 0.75 x FVC.


CONCLUSIONS
These two new predicting formulae for %FEV(1)/FVC and %FEV(3)/FVC, which require only age and FVC as variables, approximate actual values closer than previously published separate formulae for each ethnicity and sex. With 95% confidence limits, they should allow better discrimination between normality and airway obstruction in adults of at least these three ethnicities.
Hansen
James E
JE
Division of Respiratory and Critical Care Physiology and Medicine, Department of Medicine, Los Angeles Biomedical Institute at Harbor-UCLA Medical Center, Torrance, CA 90509, USA. jhansen@labiomed.org
Sun
Xing-Guo
XG
Wasserman
Karlman
K
D000328:Adult; D001741:Black or African American / Q000706:statistics & numerical data*; D000367:Age Factors; D000368:Aged; D000465:Algorithms; D005260:Female; D005541:Forced Expiratory Volume / Q000502:physiology; D006630:Hispanic or Latino / Q000706:statistics & numerical data*; D006801:Humans; D008173:Lung Diseases, Obstructive / Q000175:diagnosis* / Q000453:epidemiology / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D009749:Nutrition Surveys; D011237:Predictive Value of Tests; D012737:Sex Factors; D014797:Vital Capacity / Q000502:physiology; D044465:White People / Q000706:statistics & numerical data*