Underestimation of airflow obstruction among young adults using FEV1/FVC <70% as a fixed cut-off: a longitudinal evaluation of clinical and functional outcomes

Thorax. 2008 Dec;63(12):1040-5. doi: 10.1136/thx.2008.095554. Epub 2008 May 20.

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.

Publication types

  • Multicenter Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Airway Obstruction / diagnosis*
  • Airway Obstruction / psychology
  • Early Diagnosis
  • Female
  • Forced Expiratory Volume / physiology
  • Humans
  • Longitudinal Studies
  • Male
  • Prognosis
  • Reference Values
  • Smoking / physiopathology
  • Vital Capacity / physiology
  • Young Adult