Serum eosinophilic cationic protein and blood eosinophil counts for the prediction of the presence of airways inflammation in children with wheezing

Background Serum eosinophilic cationic protein (ECP) concentrations may be useful noninvasive markers of airways inflammation in atopic asthma. Howeve r, the usefulness of serum ECP measurement for the prediction of airways in flammation in children with a history of wheezing is unknown. Objective To determine the test accuracy of serum ECP and blood eosinophil percentage as noninvasive markers of eosinophilic airways inflammation. Methods Bronchoalveolar lavage (BAL) fluid and peripheral blood samples for eosinophil percentages and serum ECP were obtained from children undergoin g elective surgery and who gave a history of wheezing in the previous year. Sensitivity, specificity and likelihood ratios (LH) and the area under the curve (AUC) for the receiver operator characteristic (ROC) curve were calc ulated for each blood marker for the prediction of airways inflammation def ined by a BAL eosinophil percentage >0.86. Data were analysed on tho basis of how recently symptoms had occurred. Results Seventy-seven children (median age 6.75 years) were studied. An AUC of 0.75 (log serum ECP concentration) and 0.76 (log blood eosinophil perce ntage) was obtained for predicting airways inflammation. A serum ECP> 13 mu g/L yielded a LPI of 4.4, whereas using a cutoff blood eosinophils > 4% yi elded a LH of 1.9, for the prediction of elevated eosinophils in BAL. Serum ECP and eosinophil percentages in BAL and blood were lowest (not statistic ally significant) when last symptoms had occurred more than 12 weeks previo usly. Conclusions Serum ECP and blood eosinophil percentages are useful markers f or predicting eosinophilic airways inflammation in wheezing children.