EPIDEMIOLOGIC-STUDY OF THE GENETICS AND ENVIRONMENT OF ASTHMA, BRONCHIAL HYPERRESPONSIVENESS, AND ATOPY - PHENOTYPE ISSUES

The Epidemiological Study of the Genetics and Environment of Asthma (E G EA) combined a case-control study and a family study. The total samp le of 1,854 consisted of 348 patients with asthma selected through che st clinics and 416 control subjects and nuclear families ascertained t hrough the cases. The protocol included standardized questionnaires, b ronchial responsiveness, allergen skin-prick tests according to intern ational protocols, total serum immunoglobulin E (IgE) level measuremen ts, and blood eosinophilia. Criteria used to select subjects with asth ma and determine asthma status of relatives for affected sibling pair linkage analysis are described. Based on figures from the 348 asthma c ases of the EGEA study, issues relative to the definition of severe as thma and intermediate phenotypes such as bronchial responsiveness and allergic markers are discussed. Given the phenotypic heterogeneity inv olved, relevant phenotypes that may lead to the detection of genetic f actors will depend on the hypothesis tested. Standardization of primar y data and subphenotypes is a prerequisite for pooling data, which wil l be needed in the future to better understand the genetics and enviro nmental factors of asthma.