Assessment of eosinophil granule proteins in various body fluids: is therea relation to clinical variables in childhood asthma?

Background The eosinophil plays a central role in the inflammatory process in bronchial asthma. Recent studies have indicated that the assessment of e osinophil-derived proteins in various body fluids could be used for monitor ing disease activity of childhood asthma. Till now, no study exists which c ompared the levels of eosinophil-derived proteins in various body fluids su ch as serum, nasal lavage fluid (NALF) and urine. Objective To investigate whether eosinophil granule proteins in different c ompartments were correlated and whether there is a relationship between dis ease activity, pulmonary function and bronchial hyperreactivity. Methods Twenty-eight children with atopic bronchial asthma were recruited. Serum, NALF and urine samples were obtained and assessed for eosinophil cat ionic protein (ECP) and eosinophil protein X (EPX). The levels of eosinophi l proteins were analysed for a relationship with lung function variables, b ronchial hyperreactivity and disease activity. Eleven healthy control subje cts were used as controls. Results Median ECP and EPX concentrations in serum (31.4 and 74.8 mu g/L vs 15.8 and 24.3 mu g/L, respectively), NALF (9.9 and 44.9 mu g/L vs 0 and 2. 5 mu g/L, respectively) and urine (49.4 vs 16.5 mu g/mmol creatinine) were significantly raised in children with bronchial asthma compared with health y control subjects. In addition, ECP and EPX levels in serum and urine samp les were significantly higher in symptomatic patients compared with asympto matic subjects with asthma. Although no relationship between eosinophil-der ived proteins in serum, NALF or urine and the level of nonspecific bronchia l hyperreactivity could be detected, the concentrations of EPX in serum and urine were correlated with variables of pulmonary function. Conclusion Our findings demonstrate increased eosinophil activity in serum, NALF and urine derived from children with bronchial asthma. Due to the rel ationship between levels of eosinophil proteins in serum/urine samples and lung function, as well as significant concentration differences between sym ptomatic and asymptomatic asthmatic children, the assessment of eosinophil proteins in serum or urine samples appear to be more appropriate in monitor ing disease activity than measurement of ECP or EPX in NALF. Thus, the dete rmination of serum ECP/EPX or urinary EPX may be preferentially used in mon itoring eosinophilic inflammation in childhood asthma.