Urinary eosinophil protein X in children: the relationship to asthma and atopy and normal values

Background: In epidemiologic studies, it may be difficult to identify child ren with bronchial asthma. Since this is the most common chronic respirator y disease in childhood, and its prevalence is still increasing, reliable me thods for identification of asthmatic children are required. This study eva luates the use of urinary eosinophil protein X (U-EPX) in epidemiologic stu dies in identifying atopic and asthmatic children. Methods: U-EPX was measured in 877 Austrian schoolchildren. The skin prick test (SPT) was performed with eight common aeroallergens, and established q uestionnaires were used to assess respiratory symptoms. Results: Of our cohort, 2.8% reported physician-diagnosed asthma, 5.1% repo rted wheezing within the last 12 months, and 24.1% were found to be atopic. In children with physician-diagnosed asthma, as well as in atopic children (positive SPT), median U-EPX levels were significantly higher than in heal thy subjects (142.8 and 89.6 vs 63.9 mu g/mmol creatinine, P < 0.0001 and P < 0.0001, respectively). In addition, perennial sensitization to inhalant allergens resulted in higher U-EPX levels than did seasonal sensitization. The odds ratio for U-EPX levels over the 90th percentile was significantly elevated for asthma, for wheezing, for nocturnal cough, and for breathlessn ess at exercise, as well as for seasonal and perennial sensitization. Pulmo nary function was negatively related to U-EPX levels. Conclusions: Measurement of U-EPX, which can be obtained easily, may be hel pful in diagnosing both asthma and atopy in children. However, there is a g reat overlap between controls and symptomatics, a fact which reduces the se nsitivity of U-EPX in determination of the prevalence of asthma in epidemio logic studies.