title: Spirometric criteria for airway obstruction: Use percentage of FEV1/FVC ratio below the fifth percentile, not < 70%.
abstract: BACKGROUND
  Current authoritative spirometry guidelines use conflicting percentage of FEV1/FVC ratios (FEV1/FVC%) to define airway obstruction. The American Thoracic Society/European Respiratory Society Task Force characterizes obstruction as a FEV1/FVC% below the statistically defined fifth percentile of normal. However, many recent publications continue to use the Global Initiative for Chronic Obstructive Lung Disease (GOLD) primary criterion that defines obstruction as a FEV1/FVC% < 70%. Data from the Third National Health and Nutrition Examination Survey (NHANES-III) should identify and quantify differences, help resolve this conflict, and reduce inappropriate medical and public health decisions resulting from misidentification.
  
  
  METHODS
  Using these two guidelines, individual values of FEV1/FVC% were compared by decades in 5,906 healthy never-smoking adults and 3,497 current-smokers of black (African American), Hispanic (Latin), or white ethnicities aged 20.0 to 79.9 years.
  
  
  RESULTS
  In the never-smoking population, the lower limits of normal used in other reference equations fit reasonably well the NHANES-III statistically defined fifth percentile guidelines. But nearly one half of young adults with FEV1/FVC% below the NHANES-III fifth percentile of normal were misidentified as normal because their FEV1/FVC% was > 70% (abnormals misidentified as normal). Approximately one fifth of older adults with observed FEV1/FVC% above the NHANES-III fifth percentile had FEV1/FVC% ratios < 70% (normals misidentified as abnormal).
  
  
  CONCLUSIONS
  The GOLD guidelines misidentify nearly one half of abnormal younger adults as normal and misidentify approximately one fifth of normal older adults as abnormal.
authors.affiliation: Division of Respiratory and Critical Care Physiology and Medicine, Department of Medicine, Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, CA 90509. jhansen@labiomed.org
authors.forename: James E
authors.initials: JE
authors.lastname: Hansen
authors.forename: Xing-Guo
authors.initials: XG
authors.lastname: Sun
authors.forename: Karlman
authors.initials: K
authors.lastname: Wasserman
mesh_terms: D000328:Adult; D001741:Black or African American; D000368:Aged; D005260:Female; D005541:Forced Expiratory Volume / Q000502:physiology; D006630:Hispanic or Latino; D006801:Humans; D008173:Lung Diseases, Obstructive / Q000175:diagnosis* / Q000208:ethnology / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D009749:Nutrition Surveys; D017410:Practice Guidelines as Topic; D011237:Predictive Value of Tests; D012907:Smoking / Q000503:physiopathology*; D013147:Spirometry; D014481:United States; D014797:Vital Capacity / Q000502:physiology; D044465:White People