The clinical use of urinary eosinophil protein X (U-EPX) measurements in monitoring inflammation in childhood asthma was investigated. U-EPX and pulmonary function were assessed in 80 children with bronchial asthma and 24 healthy, age-matched controls. In addition, 14 patients with asthma were re-examined after 1-2 months. U-EPX levels were increased in children with asthma compared with controls (median 68.4 vs 35.3 micrograms/mmol creatinine; P < 0.0001). In addition, U-EPX levels were higher in symptomatic than in asymptomatic patients (median 123.5 vs 48.9 micrograms/mmol creatinine; P < 0.0001) independent of treatment modalities (i.e., inhaled steroids or disodium cromoglycate) or atopy (median 65.1 vs 86.0 micrograms/mmol creatinine). Furthermore, U-EPX levels were significantly correlated with pulmonary function. During the follow-up period, changes in U-EPX values were significantly related to changes in pulmonary function. In conclusion, our findings demonstrate that eosinophil activation can be measured in urine in childhood asthma. Concentrations of U-EPX are related to disease activity and pulmonary function, as shown in both cross-sectional and longitudinal analyses, but are independent of atopy and treatment modalities. Measurement of U-EPX may be useful in assessing the inflammatory process and therefore in the management of childhood asthma.

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