Bronchial responsiveness and serum eosinophil cationic protein levels in preschool children with recurrent wheezing

Background: Bronchial hyperresponsiveness is a universally recognized phenomenon of asthma, and increased levels of eosinophil cationic protein (ECP) have been identified in the serum of patients with asthma. Objectives: To investigate whether enhanced bronchial responsiveness and elevated serum ECP levels are associated with recurrent wheezing in preschool children and to examine the possible relationship between these 2 variables. Methods: We recruited 130 children aged 4 to 6 years: 59 with at least 3 episodes of wheezing in the previous year (current wheezers), 38 with a documented history of wheezing before 3 years of age but no subsequent wheezing episodes (past wheezers), and 33 who had never experienced wheezing (nonwheezers). The children underwent methacholine bronchial provocation tests using a modified auscultation method and blood sampling for the measurement of ECP levels. Results: Current wheezers showed greater bronchial responsiveness than past wheezers and nonwheezers, as demonstrated by lower provocation concentrations that caused audible wheeze and lower provocation concentrations that caused a decline in oxygen saturation of at least 5% from baseline. Likewise, current wheezers had higher serum ECP levels than the other 2 groups. Among current wheezers, ECP levels showed a significant negative correlation with provocation concentrations that caused oxygen desaturation and a marginally significant correlation with provocation concentrations that caused audible wheeze. Conclusions: Enhanced bronchial responsiveness and elevated serum ECP levels are associated with recurrent wheezing in 4- to 6-year-old children. These results suggest that wheezing during preschool years may be phenotypically similar to wheezing in older children.