title: Longitudinal study of grass pollen exposure, symptoms, and exhaled nitric oxide in childhood seasonal allergic asthma.
abstract: BACKGROUND
  Exhaled nitric oxide (NO) has been proposed as a marker of airway eosinophilic inflammation in asthma. There is currently a paucity of longitudinal data relating it to allergen exposure and asthma symptoms.
  
  
  METHODS
  Forty four children (6-16 years) with seasonal allergic asthma were sequentially followed before and during the grass pollen season. Asthma symptoms, lung function, NO levels, and pollen counts were recorded. The relationship between exhaled NO and both the pollen levels and asthma control were assessed longitudinally, comparing a subject's measurements with their previous ones.
  
  
  RESULTS
  The median exhaled NO concentration was significantly increased during the pollen season (6.2 v 9.2 parts per billion (ppb), p<0.002; median change 2.9 ppb, 95% confidence interval 1.5 to 5.4). Exhaled NO was best associated with the mean pollen count in the week before measurement. It was also significantly associated with asthma control.
  
  
  CONCLUSIONS
  The results suggest that, within a longitudinal model, the exhaled NO concentration is related to preceding allergen exposure and asthma control. It may be clinically more useful to compare exhaled NO values with a subject's previous values than to compare them with a population based normal range.
authors.affiliation: Paediatric Allergy, Asthma and Immunology, Imperial College of St Mary's, London, UK.
authors.forename: G
authors.initials: G
authors.lastname: Roberts
authors.forename: C
authors.initials: C
authors.lastname: Hurley
authors.forename: A
authors.initials: A
authors.lastname: Bush
authors.forename: G
authors.initials: G
authors.lastname: Lack
mesh_terms: D000293:Adolescent; D000485:Allergens / Q000009:adverse effects*; D001249:Asthma / Q000209:etiology*; D001944:Breath Tests; D002648:Child; D005260:Female; D005541:Forced Expiratory Volume / Q000502:physiology; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D009569:Nitric Oxide / Q000032:analysis*; D006109:Poaceae; D011058:Pollen / Q000009:adverse effects*; D006255:Rhinitis, Allergic, Seasonal / Q000209:etiology; D012621:Seasons
chemical_list: D000485:Allergens; D009569:Nitric Oxide