Table 3 The prevalence (as a percentage) of airway obstruction in three large population based samples using three reference equations and different definitions of airway obstruction applied to each population
AgenFEV1/FVC <0.70FEV1/FVC <LLNFEV1/FVC <LLN and FEV1 <80%pred
    <5014 5066.
    ⩾5010 09824.015.717.
    All24 60413.411.914.
  • Different definitions of airway obstruction include: the GOLD criterion; FEV1/FVC below the LLN for three reference equations; and the last three columns apply the FEV1% pred <80% (BTS and NICE) criteria together with the FEV1/FVC <LLN criteria for each reference equation.

  • The most appropriate reference equations are internal to the study (indicated by the bold numbers). Analysis in Americans was limited to Caucasian subjects. Reference equation sources: NHANES III26 and HSE.20 NL is the Dutch reference equations (see appendix in the online data supplement).

  • BTS, British Thoracic Society; FEV1/FVC, forced expiratory volume in 1 s/forced vital capacity; GOLD, Global Initiative for Chronic Obstructive Lung Disease; HSE, Health Survey for England; LLN, lower limit of normal; NICE, National Institute for Health and Clinical Excellence; NHANES III, National Health and Nutrition Examination Survey III.