Prevalence of atopy and range of bronchial response to methacholine in 7 and 11 year old schoolchildren.

A sample of 397 from 2503 children aged 7 and 11 years, who took part in an earlier questionnaire study of respiratory symptoms in Southampton, was chosen for methacholine bronchial provocation and allergen skin testing. Results were obtained from 330 (84%). A good level of repeatability was achieved for bronchial provocation testing giving a 95% confidence interval equivalent to 1.74 doubling concentrations. The main problem encountered with methacholine was its bitter taste in high concentrations. The proportion of children, in whom the dose of methacholine which produced a fall of 20% in the forced expiratory volume in one second (PD20 methacholine) was less than or equal to 6.4 mumol, fell from 29.1% at 7 years to 16.5% at 11 years. The prevalence of atopy increased from 26% at 7 years to 31.6% at 11 years. A highly significant association was found between bronchial responsiveness to methacholine and atopy, which was independent of symptoms or age group.