Epidemiologic methods for measuring prevalence of asthma.

Problems identified as associated with measuring the prevalence of asthma include the lack of an agreed definition, absence of standardization of questionnaires (both the content and the form in which questions are worded) the nonspecific nature of tests of bronchial responsiveness and the variation in the nature of asthma at different ages, seasonally and due to occupational exposures. Approaches to the resolution of these problems and outstanding questions are discussed.