Enhancing validity: what counts as an asthma attack?
BACKGROUND: Major epidemiological studies in asthma use the question: "How many attacks of asthma have you had in the last 12 months?" We set out to study what constitutes an asthma attack from the perspective of people with asthma. We also examined concordance between qualitative responses and standard quantitative measures of this question. METHODS: Individuals aged 18 to 70 years who sought care for asthma at Emergency Departments in an Australian central city, a suburban and a regional hospital were recruited. Sixty two (43 women and 19 men) participants were interviewed in depth. All interviews were taped, transcribed and thematically analyzed. Demographic data and responses to respiratory health data were also collected. FINDINGS: Widely varying responses to the question, "How many attacks of asthma have you had in the last 12 months?" were found in the quantitative data set. Comparison of quantitative and qualitative data sets showed good agreement between these two responses (intraclass correlation 0.66). People defined asthma attacks as "major" and "minor," as determined by the degree of personal control they were able to exercise. A strongly unifying description of a severe attack was that it was "out of control." Patient's recognized that upper respiratory tract infections commonly triggered major attacks. INTERPRETATION: A commonly asked question about the number of asthma attacks in the past year needs refinement in order to enhance validity. Asthma action plans should use the words "out of control" when defining a severe attack of asthma.