title: The ratio of FEV1 to FVC as a basis for establishing chronic obstructive pulmonary disease.
abstract: BACKGROUND
  The lambda-mu-sigma (LMS) method is a novel approach that defines the lower limit of normal (LLN) for the ratio of FEV1/FVC as the fifth percentile of the distribution of Z scores. The clinical validity of this threshold as a basis for establishing chronic obstructive pulmonary disease is unknown.
  
  
  OBJECTIVE
  To evaluate the association between the LMS method of determining the LLN for the FEV1/FVC, set at successively higher thresholds, and clinically meaningful outcomes.
  
  
  METHODS
  Using data from a nationally representative sample of 3,502 white Americans aged 40-80 years, we stratified the FEV1/FVC according to the LMS-LLN, with thresholds set at the 5th, 10th, 15th, 20th, and 25th percentiles (i.e., LMS-LLN5, LMS-LLN10, etc.). We then evaluated whether these thresholds were associated with an increased risk of death or prevalence of respiratory symptoms. Spirometry was not specifically completed after a bronchodilator.
  
  
  RESULTS
  Relative to an FEV1/FVC greater than or equal to LMS-LLN25 (reference group), the risk of death and the odds of having respiratory symptoms were elevated only in participants who had an FEV1/FVC less than LMS-LLN(5), with an adjusted hazard ratio of 1.68 (95% confidence interval, 1.34-2.12) and an adjusted odds ratio of 2.46 (95% confidence interval, 2.01-3.02), respectively, representing 13.8% of the cohort. Results were similar for persons aged 40-64 years and those aged 65-80 years.
  
  
  CONCLUSIONS
  In white persons aged 40-80 years, an FEV1/FVC less than LMS-LLN5 identifies persons with an increased risk of death and prevalence of respiratory symptoms. These results support the use of the LMS-LLN5 threshold for establishing chronic obstructive pulmonary disease.
authors.affiliation: Yale Claude D. Pepper Older Americans Independence Center, New Haven, Connecticut, USA. carlos.fragoso@yale.edu
authors.forename: Carlos A
authors.initials: CA
authors.lastname: Vaz Fragoso
authors.forename: John
authors.initials: J
authors.lastname: Concato
authors.forename: Gail
authors.initials: G
authors.lastname: McAvay
authors.forename: Peter H
authors.initials: PH
authors.lastname: Van Ness
authors.forename: Carolyn L
authors.initials: CL
authors.lastname: Rochester
authors.forename: H Klar
authors.initials: HK
authors.lastname: Yaggi
authors.forename: Thomas M
authors.initials: TM
authors.lastname: Gill
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D016009:Chi-Square Distribution; D005260:Female; D005541:Forced Expiratory Volume / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D016016:Proportional Hazards Models; D029424:Pulmonary Disease, Chronic Obstructive / Q000175:diagnosis* / Q000453:epidemiology / Q000503:physiopathology; D012016:Reference Values; D012737:Sex Factors; D014481:United States / Q000453:epidemiology; D014797:Vital Capacity / Q000502:physiology*