Defining airflow obstruction

Margaret Smith, Om Kurmi

Research output: Contribution to journalArticlepeer-review


Our paper investigated airflow obstruction (AFO) in never-smokers in the China Kadoorie Biobank (CKB) [1]. We presented prevalence of AFO overall, by age and sex, and by region according to both fixed ratio (forced expiratory volume in 1 s (FEV1)/forced vital capacity (FVC) <0.7) and lower limit of normal (LLN) criteria (FEV1/FVC <fifth percentile). For overall prevalence and prevalence by region we also subdivided the prevalence defined by the fixed ratio according to FEV1 ≥80% predicted. We calculated odds ratios for associations of all variables with both the fixed ratio definition of AFO and the LLN definition, but chose to present the former. We found that prevalence according to the LLN definition when compared with the fixed ratio was considerably higher (for the reasons given by P.H. Quanjer and co-authors). For women, the LLN definition resulted in a higher prevalence than the fixed ratio definition up to age 65–69 years, and the excess was greatest among those with a lower baseline age.
Original languageEnglish
Pages (from-to)563-564
Number of pages2
JournalEuropean Respiratory Journal
Issue number2
Publication statusPublished - Feb 2015
Externally publishedYes


  • Asthma/diagnosis
  • Female
  • Humans
  • Male
  • Pulmonary Disease, Chronic Obstructive/diagnosis


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