Urinary excretion of leukotriene E4 and eosinophil protein X in children with atopic asthma.

Measurement of leukotriene E4 (LTE4) in urine is a noninvasive method for assessing changes in the rate of total body cysteinyl leukotriene production. Eosinophil protein X (EPX) has been used to assess eosinophil activity and monitor inflammation in bronchial asthma. The aim of the study was to look for differences in urinary LTE4 and EPX concentrations between children with stable atopic asthma and healthy controls and to compare asthmatic children with different disease severity. In addition the relationship was evaluated between urinary LTE4 and EPX levels and lung function. LTE4 was also measured (enzyme immunoassay) together with EPX (radioimmunoassay) in urine and lung function tests were carried out in children with mild asthma (steroid-naive) (n=49), moderate to severe asthma (using inhaled steroids) (n=31) and healthy control subjects (n=28). Urinary leukotriene E4 (LTE4) was significantly higher in children with asthma than in controls (median [25-75 percentile] 238.5 (126.5-375.7) SD 191.8 versus 189 (51-253.2) SD 131.7 pg.mg(-1) creatinine; p=0.021). Urinary EPX was also significantly increased in asthmatic children compared with controls (85.5 [64-131.5] SD 76.2 versus 48.5 [43.2-90] 112.1 microg x mmol(-1) creatinine; p=0.006). There were no differences in urinary LTE4 and EPX between the group of mild and the group of moderate to severe asthmatic children. There were significant associations between the urinary LTE4 and intrathoracic gas volume (ITGV), residual volume (RV), forced expiratory volume in one second (FEV1), forced expiratory capacity (FVC) and maximum expiratory flow rate at 25% of vital capacity (MEF25). Urinary EPX was only correlated with maximum expiratory flow rate at 75% of vital capacity (MEF75). Thus measurement of urinary LTE4 may predict the degree of airflow obstruction in asthmatic children. Urinary LTE4 and EPX are useful markers of airway inflammation and can be helpful in guiding asthma management. There was no correlation between LTE4 and EPX levels.