title: Which clinical subgroups within the spectrum of child asthma are attributable to atopy?
abstract: OBJECTIVE
  The contribution of atopy to childhood asthma has been debated. We aimed to examine the relationship between atopy and asthma, taking into account differences in respiratory symptoms and disease severity.
  
  
  METHODS
  A cross-sectional asthma survey involving the following: (1) a population sample of 758 (81% of eligible) school children aged 8 to 10 years from randomly selected schools in the Australian Capital Territory in 1999, and (2) a hospital-based sample of 78 (70% of eligible) children attending the hospital for asthma. Skin-prick test results to 10 common aeroallergens were available on 722 children and 77 children, respectively. Baseline spirometry was obtained on a subset of school children (n = 515, 78% of eligible).
  
  
  RESULTS
  The association between atopy and wheeze by wheeze frequency over the past year was as follows: no episodes (odds ratio [OR], 1.00 [reference]), 1 to 3 episodes (OR, 3.27; 95% confidence interval [CI], 2.15 to 4.97), 4 to 12 episodes (OR, 3.44; 95% CI, 1.75 to 6.75), and > 12 episodes (OR, 8.70; 95% CI, 3.07 to 24.55), with a higher population attributable fraction (PAF) for > 12 episodes (75%) than 1 to 3 episodes (49%). Atopy was moderately related to asthma ever (OR, 2.09; 95% CI, 1.52 to 2.85; PAF, 33%) but strongly related to 1999 hospital attendance for asthma (OR, 16.95; 95% CI, 6.76 to 42.48; PAF, 89%). Adjustment for child age, gas heater use, and maternal smoking near the child did not materially alter these findings.
  
  
  CONCLUSIONS
  The clinical features of frequent wheeze or hospital asthma attendance are largely attributable to atopy, but infrequent wheeze or a history of asthma ever are not. Atopic children are overrepresented in the severe range of the asthma spectrum.
authors.affiliation: National Center for Epidemiology and Population Health, Australian National University, Australian Capital Territory, Australia. anne-louise.ponsonby@anu.edu.au
authors.forename: Anne-Louise
authors.initials: AL
authors.lastname: Ponsonby
authors.forename: Paul
authors.initials: P
authors.lastname: Gatenby
authors.forename: Nicholas
authors.initials: N
authors.lastname: Glasgow
authors.forename: Raymond
authors.initials: R
authors.lastname: Mullins
authors.forename: Tim
authors.initials: T
authors.lastname: McDonald
authors.forename: Mark
authors.initials: M
authors.lastname: Hurwitz
mesh_terms: D001249:Asthma / Q000175:diagnosis / Q000453:epidemiology*; D020958:Australian Capital Territory / Q000453:epidemiology; D002648:Child; D015897:Comorbidity; D003430:Cross-Sectional Studies; D005260:Female; D006306:Health Surveys; D006801:Humans; D015994:Incidence; D008297:Male; D012130:Respiratory Hypersensitivity / Q000175:diagnosis / Q000453:epidemiology*