title: The diagnostic importance of a reduced FEV1/FEV6.
abstract: BACKGROUND
  On spirometry the FEV(1)/FEV(6) ratio has been advocated as a surrogate for the FEV(1)/FVC. The significance of isolated reductions in either the FEV(1)/FEV(6) or FEV(1)/FVC is not known.
  
  
  METHODS
  First-time adult spirograms (n = 22,837), with concomitant lung volumes (n = 12,040), diffusion (n = 14,154), and inspiratory capacity (n = 12,480) were studied. Four groups were compared. 1) Only FEV(1)/FEV(6) reduced (n = 302). 2) Only FEV(1)/FVC reduced (n = 1158). 3) Both ratios reduced (n = 6593). 4) Both ratios normal (n = 14,784).
  
  
  RESULTS
  In patients with obstructed spirometry (either a reduced FEV(1)/FVC and/or FEV(1)/FEV(6)), 3.8% only had a reduced FEV(1)/FEV(6), while 14.4% only had a reduced FEV(1)/FVC. The mean FEV(1) was lower when both ratios were reduced. The group with only a reduced FEV(1)/FEV(6), compared to only the FEV(1)/FVC reduced, had a lower FEV(1), FVC, BMI, Expiratory Time, and IC (p values < 0.0001). DL(CO) was also lower (p = 0.005), and the FEV(1)/FVC and RV/TLC were higher (p values < 0.0001). When the patients with only a reduced FEV(1)/FEV(6) had a subsequent spirogram, 60% had a reduced FEV(1)/FVC when their mean expiratory times were 3.5 seconds longer. Ninety percent of this group had strong clinical evidence of airways obstruction.
  
  
  CONCLUSIONS
  The FEV(1)/FEV(6) is not as sensitive as the FEV(1)/FVC for diagnosing airways obstruction, but in the presence of a normal FEV(1)/FVC, subjects have greater physiologic abnormalities than when only the FEV(1)/FVC is reduced. The FEV(1)/FEV(6) ratio should not replace the FEV(1)/FVC as the standard for airways obstruction, but there is benefit including this measurement to identify individuals with greater air trapping and diffusion abnormalities.
authors.affiliation: Henry Ford Health System, Division of Pulmonary and Critical Care Medicine, Detroit, Michigan, USA. zmorris1@hfhs.org
authors.forename: Zachary Q
authors.initials: ZQ
authors.lastname: Morris
authors.forename: Najia
authors.initials: N
authors.lastname: Huda
authors.forename: Robert R
authors.initials: RR
authors.lastname: Burke
mesh_terms: D000328:Adult; D000402:Airway Obstruction / Q000175:diagnosis* / Q000503:physiopathology; D001249:Asthma / Q000175:diagnosis / Q000503:physiopathology; D001987:Bronchiectasis / Q000175:diagnosis / Q000503:physiopathology; D045853:Exhalation / Q000502:physiology; D005260:Female; D005541:Forced Expiratory Volume / Q000502:physiology*; D006801:Humans; D008297:Male; D010991:Plethysmography; D029424:Pulmonary Disease, Chronic Obstructive / Q000175:diagnosis / Q000503:physiopathology; D012907:Smoking / Q000503:physiopathology; D013147:Spirometry; D014135:Tracheal Stenosis / Q000175:diagnosis / Q000503:physiopathology; D014797:Vital Capacity / Q000502:physiology