Response-dose ratio as an index of bronchial responsiveness to hypertonic saline challenge in an epidemiological survey of asthma in Polish children.

Abstract

This epidemiological survey was done to evaluate the bronchial responsiveness (BHR) to a 4.5% hypertonic saline (HS) challenge in 13-14 year-old schoolchildren. BHR was measured by the response-dose ratio in which the response was estimated by the decline of FEV1 index of BHR (IxFEV1). Validity of the HS challenge test as a screening test for confirmation of reported asthma symptoms and the diagnosis of asthma was assessed. With a cutoff of 90th percentile of IxFEV1 in controls, the test sensitivity and specificity for asthma symptoms in the last 12 months was 44% and 90%, respectively. For the diagnosis of asthma the test sensitivity was 67% and specificity 90%. The mean log transform of IxFEV1 was significantly higher in children with more than three episodes of wheezing in the last 12 months and a diagnosis of asthma than in controls. Moreover, in the group with more than three episodes of asthma in the last 12 months the mean IxFEV1 was higher in girls than in boys. There was no gender difference in other groups of asthmatic children and controls. In Polish schoolchildren the prevalence of BHR to HS was 12.5% when adjusted to the prevalence of wheezing in the last 12 months. By multiple linear regression analysis, factors associated with BHR were serum levels of total IgE in children and of maternal IgE, as well as children's peripheral blood eosinophil counts. Also, the size of skin reaction to mite and dog allergens correlated with BHR.