PREVALENCE OF BRONCHIAL HYPERRESPONSIVENESS TO 4.5-PERCENT SALINE ANDITS RELATION TO ASTHMA AND ALLERGY SYMPTOMS IN AUSTRIAN CHILDREN

The prevalence of asthma in school children has been reported to have increased with wide variations between countries. To allow comparison of prevalence data, objective markers of asthma should be measured. Th erefore, we assessed the prevalence of bronchial hyperresponsiveness ( BHR) to hypertonic saline and its relation to asthma and allergy sympt oms in 507 Austrian school children, aged 12-15 yrs in a cross-section al, community based survey. These children were selected from 3,371 ch ildren who had answered a self-administered written questionnaire on a sthma, hay fever, eczema and environmental factors. The prevalence of BHR to hypertonic saline was 14% and the majority (70%) of the childre n had mild BHR. The prevalence of wheeze in the last 12 months was 12% and of a diagnostic label of asthma was 6%. Fifty three per cent of t he children with symptoms in the last 12 months and a diagnostic label of asthma had BHR, and 33% of those with symptoms in the last 12 mont hs regardless of a diagnostic label of asthma showed a positive respon se to hypertonic saline. Atopic dermatitis, a diagnostic label of asth ma, night cough apart from colds, wheeze in the past 12 months (but no t ''former wheeze'') and male gender were significantly associated wit h increased response to 4.5% saline in the final logistic regression m odel. These results show that the prevalence of asthma symptoms in the last 12 months and the prevalence of bronchial hyperresponsiveness to hypertonic saline are twice that of a diagnosis of asthma and that as thma might be underdiagnosed in the present population. The response t o hypertonic saline is most strongly associated with current asthma an d allergy symptoms. A combination of a ''diagnostic label of asthma'' and ''asthma symptoms in the last 12 months'' might best reflect ''cur rent asthma'' in epidemiological studies in this population.