title: Prevalence of asthma, atopy and bronchial hyperresponsiveness and their interrelation in a semi-rural area of Chile.
abstract: OBJECTIVE
  To assess the prevalence of asthma symptoms and their association with sensitisation to eight allergens and bronchial hyperresponsiveness (BHR) to methacholine.
  
  
  METHODS
  A random sample of 1232 adults, aged 22 to 28 years, studied in a Chilean semi-rural area.
  
  
  METHODS
  A cross-sectional design for the purpose of this analysis.
  
  
  RESULTS
  The prevalence of wheeze was 27.4% (95%CI 24.9-29.9) and waking with breathlessness 13.7% (95%CI 11.8-15.6), higher than the results of a multi-centre European study. Only 7.8% (95%CI 6.3-9.3) had a positive BHR (< or =8 mg/ml) and 26.3% (95%CI 23.8-28.8) were atopic. The Youden index of asthma symptoms in non-atopic subjects varied from 0.184 to 0.259 when using BHR as gold standard for asthma, and increased from 0.379 to 0.504 among those with positive atopy. Only 4.5% reported asthma, and the Youden index was slightly higher in comparison to the asthma symptom groups.
  
  
  CONCLUSIONS
  The prevalence of asthma symptoms in young adults was high, but only a small proportion of these were sensitised or had a positive BHR. We believe that aetiological studies of asthma should analyse subjects with asthma symptoms separately from those with positive atopic status or positive BHR.
authors.affiliation: Department of Paediatrics, Faculty of Medicine University of Chile, Independencia 1027, Santiago 8389100, Chile. jmackenney@med.uchile.cl
authors.forename: J
authors.initials: J
authors.lastname: Mackenney
authors.forename: M J
authors.initials: MJ
authors.lastname: Oyarzun
authors.forename: P V
authors.initials: PV
authors.lastname: Diaz
authors.forename: R
authors.initials: R
authors.lastname: Bustos
authors.forename: H
authors.initials: H
authors.lastname: Amigo
authors.forename: R J
authors.initials: RJ
authors.lastname: Rona
mesh_terms: D000328:Adult; D001249:Asthma / Q000453:epidemiology*; D016535:Bronchial Hyperreactivity / Q000453:epidemiology*; D002677:Chile / Q000453:epidemiology; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D006969:Hypersensitivity, Immediate / Q000453:epidemiology*; D008297:Male; D015995:Prevalence; D012423:Rural Health