title: Underestimation of airflow obstruction among young adults using FEV1/FVC <70% as a fixed cut-off: a longitudinal evaluation of clinical and functional outcomes.
abstract: BACKGROUND
  Early detection of airflow obstruction is particularly important among young adults because they are more likely to benefit from intervention. Using the forced expiratory volume in 1 s (FEV(1)) to forced vital capacity (FVC) (FEV(1)/FVC) <70% fixed ratio, airflow obstruction may be underdiagnosed. The lower limit of normal (LLN), which is statistically defined by the lower fifth percentile of a reference population, is physiologically appropriate but it still needs a clinical validation.
  
  
  METHODS
  To evaluate the characteristics and longitudinal outcomes of subjects misidentified as normal by the fixed ratio with respect to the LLN, 6249 participants (aged 20-44 years) in the European Community Respiratory Health Survey were examined and divided into three groups (absence of airflow obstruction by the LLN and the fixed ratio; presence of airflow obstruction only by the LLN; presence of airflow obstruction by the two criteria) for 1991-1993. LLN equations were obtained from normal non-smoking participants. A set of clinical and functional outcomes was evaluated in 1999-2002.
  
  
  RESULTS
  The misidentified subjects were 318 (5.1%); only 45.6% of the subjects with airflow obstruction by the LLN were also identified by the fixed cut-off. At baseline, FEV(1) (107%, 97%, 85%) progressively decreased and bronchial hyperresponsiveness (slope 7.84, 6.32, 5.57) progressively increased across the three groups. During follow-up, misidentified subjects had a significantly higher risk of developing chronic obstructive pulmonary disease and a significantly higher use of health resources (medicines, emergency department visits/hospital admissions) because of breathing problems than subjects without airflow obstruction (p<0.001).
  
  
  CONCLUSIONS
  Our findings show the importance of using statistically derived spirometric criteria to identify airflow obstruction.
authors.affiliation: Division of Respiratory Diseases, IRCCS San Matteo Hospital Foundation, University of Pavia, Pavia, Italy.
authors.forename: I
authors.initials: I
authors.lastname: Cerveri
authors.forename: A G
authors.initials: AG
authors.lastname: Corsico
authors.forename: S
authors.initials: S
authors.lastname: Accordini
authors.forename: R
authors.initials: R
authors.lastname: Niniano
authors.forename: E
authors.initials: E
authors.lastname: Ansaldo
authors.forename: J M
authors.initials: JM
authors.lastname: Antó
authors.forename: N
authors.initials: N
authors.lastname: Künzli
authors.forename: C
authors.initials: C
authors.lastname: Janson
authors.forename: J
authors.initials: J
authors.lastname: Sunyer
authors.forename: D
authors.initials: D
authors.lastname: Jarvis
authors.forename: C
authors.initials: C
authors.lastname: Svanes
authors.forename: T
authors.initials: T
authors.lastname: Gislason
authors.forename: J
authors.initials: J
authors.lastname: Heinrich
authors.forename: J P
authors.initials: JP
authors.lastname: Schouten
authors.forename: M
authors.initials: M
authors.lastname: Wjst
authors.forename: P
authors.initials: P
authors.lastname: Burney
authors.forename: R
authors.initials: R
authors.lastname: de Marco
mesh_terms: D000328:Adult; D000402:Airway Obstruction / Q000175:diagnosis* / Q000523:psychology; D042241:Early Diagnosis; D005260:Female; D005541:Forced Expiratory Volume / Q000502:physiology; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D011379:Prognosis; D012016:Reference Values; D012907:Smoking / Q000503:physiopathology; D014797:Vital Capacity / Q000502:physiology; D055815:Young Adult