Comparison of Three Definitions of Asthma: A Longitudinal Perspective

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Abstract
In epidemiological studies, defining “current asthma” as the presence of both wheeze in the last year and airway hyperresponsiveness (AHR) identifies children with more severe abnormality compared with children with either measure alone. The predictive value of this definition of asthma and other commonly used definitions have not been compared. In 1982, we enrolled a random sample of 718 schoolchildren aged 8–10 years, and in 1992, we restudied a representative sample of 407. On both occasions, we measured wheeze, medication use, morbidity, AHR, and atopy. We compared three asthma definitions—“current asthma,” recent wheeze, and doctor-diagnosed asthma. Approximately 70% of subjects classified by each definition remained consistently classified in 1992. However, the current asthma definition distinguished a group with more severe illness after 10 years than did the other asthma definitions. The current asthma definition not only differentiates children with more severe asthma, but also differentiates those with a more severe prognosis.