Background: Eosinophil cationic protein (ESP) is one of the granule proteins in eosinophilic granulocytes. Release of this protein may reflect the activity state of eosinophilic granulocytes in diseased subjects. The purpose of this study was to evaluate the additional value of serum ECP measurement over the eosinophil count, (specific) IgE concentration and CRP concentration in order to evaluate the effects of treatment in patients started on corticosteroids and to distinguish individual patients with asthma from healthy subjects on the basis of laboratory results.
Methods: In a longitudinal study, serial measurements of serum ECP, eosinophil count and other laboratory parameters have been evaluated and compared with spirometry and tests of bronchial hyperresponsiveness in ten asthmatic subjects. The subjects were investigated before therapy was started and 3, 6 and 9 months after the start of therapy with inhaled corticosteroids. Laboratory parameters in the patient group are compared with results obtained from a reference group of apparently healthy subjects (n=223).
Results: Statistically significant correlations are observed between blood eosinophil counts and serum ECP concentrations with the hyperresponsiveness tests PC20 (r=0.44 and r=0.46, respectively) and with a decrease in FEV(1) after exercise (r=0.66 and r=0.60, respectively). A significant difference was detected between serum ECP concentrations from the patients' group and from the reference group. However, a wide range of overlapping results was observed between the reference group and the asthmatic patients.
Conclusions: Asthma is a disease which is now more frequently treated by general practitioners. In general practice there is not always the opportunity to evaluate asthma activity by the application of hyperreactivity tests. When hyperreactivity testing is not available, measuring serum ECP concentration or eosinophil blood count would be an alternative method to monitor the effects of corticosteroid treatment. In this study the additional value of serum ECP in addition to the eosinophil count is evaluated to determine the effects of treatment in patients who started with application of corticosteroids. However, because of the analogous correlation coefficients of laboratory parameters with tests regarding hyperresponsiveness, no additional benefit of serum ECP concentration over eosinophil blood count in monitoring the effect of corticosteroids can be detected. The additional value of serum ECP concentrations and eosinophil counts to detect an asthmatic constitution for individual cases is doubtful.