DETERMINANTS OF EOSINOPHIL CATIONIC PROTEIN IN NASAL LAVAGES IN CHILDREN

Background Nasal lavages are increasingly used to assess airways infla mmation in children. However, there are no studies assessing how measu rement error as well as biological influences contribute to the concen tration of nasal inflammatory parameters in a population based survey. Objective To investigate determinants of concentration of eosinophil cationic protein (ECP) in nasal lavages we studied 147 schoolchildren (mean age 8.1 years, SD 0.6 years) by repeated nasal lavages/year over a 2 year period. Methods Standardized questionnaires were completed b y the parents each year. A skin-prick test with seven aeroallergens (b irch, cat, dog, hazel, weeds, Dermatophagoides pteronyssinus and D. fa rinae) was performed. One hundred and one children could perform valid lavages at least five times a year, As a measure of reproducibility t he intraclass coefficient of reliability was calculated. Results The i ntraclass coefficient of reliability was 0.27 over all observations su ggesting that about a quarter of total variance is due to between-subj ect variance. Taking means over each year increased reliability to 0.6 0. Linear regression analyses with ECP being the dependent variable de monstrated significant higher values for boys (beta = 12.26; P < 0.01) , children sensitized to seasonal (P = 34.27; P = 0.02) but not to per ennial allergens (P = 4.44; P = 0.57), and for children with a serous (beta = 10.01; P = 0.01) or purulent rhinitis (beta = 22.45; P < 0.001 ). Conclusion Assessment of inflammatory mediators in nasal lavages is a useful tool for epidemiological paediatric studies, However, due to the relatively high intraindividual variability of ECP concentrations multiple lavages are necessary to characterize the individual.