PREVALENCE OF BRONCHIAL HYPERREACTIVITY AS DETERMINED BY SEVERAL METHODS AMONG ESTONIAN SCHOOLCHILDREN

There is a lack of established criteria to identify asthma and bronchi al hyperreactivity (BHR) in epidemiological studies, although both con ditions appear to bear some relationship to atopy, at least in childre n. Recent studies indicate a low prevalence of atopy in former Sociali st countries in Europe, yet the prevalence of BHR has been reported to be high. We have analysed the relationship between the outcome of var ious lung function tests, atopy and clinical symptoms of bronchial ast hma in an epidemiological survey of Estonian 10-12 year old schoolchil dren. Metacholine provocation test (four steps with the cumulative dos es 100, 300, 700 and 1100 mu g), exercise challenge test and PEF-varia bility over two weeks were done in 806 children in Tallinn (coastal, i ndustrialised city) and 774 children in Tartu (inland, university town ). A positive response to the metacholine challenge test was recorded in 19% in Tallinn and in 32% in Tartu (p<0.001). A similar tendency wa s observed for a more than 15% decrease of FEV(1) in the exercise chal lenge test, i.e. 6% in Tallinn and 18% in Tartu. There was only a weak relationship between BHR, as defined by either a positive metacholine challenge and/or exercise test, diagnosed asthma and reported wheezin g. Thus, 47% of the wheezing children and 30% of the children with ast hma had negative test results. Only 17% of the children with a positiv e metacholine challenge were atopic, as defined by at least one positi ve skin prick test. In conclusion, none of the methods employed to ass ess bronchial hyperresponsiveness were very useful for the identificat ion of wheezing and asthmatic children in this epidemiological study. In contrast to the results of studies in Western Europe, most children with bronchial hyperreactivity in Estonia are not atopic.