Background In adult asthma, bronchial hyper-responsiveness (BHR) to indirect stimuli reflects eosinophilic activation more closely than BHR to stimuli that directly cause smooth muscle contraction.
Aim To assess the relationship between BHR to the indirect stimulus hypertonic saline (HS), blood eosinophil numbers, and serum eosinophilic cationic protein (ECP) in children with and without current wheeze.
Methods A cross-sectional survey among 8–13-year-old schoolchildren, using the International Study of Asthma and Allergic disease in Childhood questionnaire, bronchial challenge with HS, skin prick tests, serum IgE, blood eosinophil counts and ECP (in a subset). Based upon the presence of current wheeze (WHE) and BHR, we defined three case groups (WHE+BHR+, WHE−BHR+, WHE+BHR−) and the reference group (WHE−BHR−). By regression analyses, each case group was compared with the reference group for differences in atopic sensitization, blood eosinophil counts and serum ECP.
Results Complete data were obtained for 470 children. BHR was present in 103 children (22%), 66 being asymptomatic and 37 symptomatic. Children of all three case groups were more often atopic. Sensitization to indoor allergens particularly occurred in children with BHR, irrespective of symptoms (P<0.05).
Children with WHE+BHR+ had highest values for blood eosinophils and serum ECP (P<0.05). Children with WHE−BHR+ had less severe responsiveness. In atopic children with WHE−BHR+, serum ECP was higher than in children with WHE-BHR-(P<0.05).
Conclusions BHR to HS is associated with blood markers of eosinophilic activation, particularly in atopic children.