Three-hundred-and-ninety-seven children aged 2-59 mo presenting to the paediatric emergency departments of five public hospitals in São Paulo, Brazil, with an acute episode of lower respiratory disease were examined. The children were classified into the following diagnostic categories: acute bronchitis, acute bronchiolitis, pneumonia, asthma, post-bronchiolitis wheezing and wheezing of uncertain aetiology. Three years after the initial study, the homes of the children diagnosed as asthmatic or as having wheezing of uncertain aetiology were visited to collect information on subsequent episodes of lower respiratory disease. This paper reports the proportional incidence of different categories of lower respiratory disease and the results of an analysis to investigate clinical features that might distinguish wheezing children between those with asthma and those with an infectious disease. The predictions made for children with wheezing of uncertain aetiology were then compared with the follow-up data. Recurrent wheezing disorders (asthma, post-bronchiolitis wheezing) were common in the study sample (47% of children). Thirty-six percent of children with an initial diagnosis of wheezing of uncertain aetiology were diagnosed as asthmatic by another doctor over the next 3 y. We were unable to identify any clinical features that were useful in identifying those children likely to be diagnosed subsequently as asthmatic.
Conclusions: The use of a diagnostic category similar to that which we have called "wheezing of uncertain aetiology" might help to alert physicians early to the possibility of asthma without interfering in the management of the illness. Such a classification might also be useful in epidemiological investigations of the aetiology of lower respiratory diseases.