No association between serum eosinophil cationic protein and atopic dermatitis or allergic rhinitis in an unselected population of children

Background In order to obtain background references when dealing with serum eosinophil cationic protein (s-ECP) measurements in children with allergic diseases, population-based studies are important. The objectives of our study were to explore the strength of associations between the s-ECP level and atopic dermatitis (AD), allergic rhinitis (AR) and asthma in an unselected northern Norwegian schoolchildren population. Methods s-ECP was sampled from 396 schoolchildren aged 7-12 years from Sor-Varanger community, northern Norway as a part of a population-based study of allergy. In advance, anamnestic information concerning a history of AD, AR and asthma were obtained. The children underwent a clinical investigation, including skin prick tests and peak expiratory flow measurements, where the presence of AD, AR and asthma were evaluated. The associations of these diseases to the s-ECP values were examined in bivariate statistical analysis. Results No statistical significant associations were detected in bivariate analysis between s-ECP and AD, AR or asthma: the mean s-ECP in children without self-reported AD/AR/asthma was 4.6 mug/L [95% confidence interval (CL) 4.0-5.2]. The mean s-ECP in children with self-reported AD or AR or asthma was 5.2 mug/L (95% CI 4.1-6.2), 4.6 mug/L (95% CI 3.5-5.7) and 6.4 mug/L (95% CI 4.4-8.3), respectively. The highest mean s-ECP level was measured in children with clinically diagnosed asthma; 7.1 mug/L (95% CI 4.0-10.3). Above the 75-percentile level of s-ECP, only 17.2% of the children had a history of asthma. Conclusions In this unselected children population, the occurrence of AD or AR was not reflected by an increase in the s-ECP level. The s-ECP was increased in children with asthma, but was not statistically significant. Furthermore, the majority of children with high s-ECP values were not asthmatics. We conclude that the associations between s-ECP and allergic diseases are weak in an unselected population of children.