HYPERTONIC SALINE CHALLENGE IN AN EPIDEMIOLOGIC SURVEY OF ASTHMA IN CHILDREN

To evaluate sensitivity and specificity of a 4.5% hypertonic saline ch allenge for a diagnosis of asthma, we studied 393 schoolchildren (13 t o 15 yr of age) with ''current wheeze:' ''former wheeze,'' and without history of wheeze in a community-based, cross-sectional survey. These children were selected from 2,836 schoolchildren in 26 schools in gre ater Melbourne, Australia who completed a self-administered questionna ire on respiratory symptoms, allergic rhinitis, and eczema. Three hund red eighty-two of 393 children successfully completed a 4.5% hypertoni c saline challenge with increasing inhalation periods, and 365 of 393 performed a 6-min standardized, free running exercise challenge. The p revalence of bronchial hyperresponsiveness to hypertonic saline was 20 .4%. Sensitivity and specificity for the hypertonic saline challenge t o identify children with ''current wheeze'' were 47% and 92% respectiv ely and for the exercise challenge, 46% and 88%. The agreement of resp onse to hypertonic saline and to exercise was only moderate (kappa = 0 .43). Factors associated with increased response to hypertonic saline in a multivariate logistic regression model were a history of ''curren t wheeze:' hay fever, response to the exercise challenge, female sex, and a lower baseline predicted FEV(1). These results suggest that a 4. 5% hypertonic saline challenge shows sensitivity and specificity simil ar to a standardized exercise challenge and pharmacologic challenges a nd a higher sensitivity than cold air hyperventilation and distilled w ater to identify asthma in children in a field study. Measurement of r esponsiveness to hypertonic saline may be of value as an objective mar ker of asthma to compare prevalence studies of bronchial hyperresponsi veness and of asthma over time and between countries.