Background: Nasal lavages are increasingly used to assess airways inflammation in children. However, there are no studies assessing how measurement error as well as biological influences contribute to the concentration 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 by the parents each year. A skin-prick test with seven aeroallergens (birch, cat, dog, hazel, weeds, Dermatophagoides pteronyssinus and D. farinae) was performed. One hundred and one children could perform valid lavages at least five times a year. As a measure of reproducibility the intraclass coefficient of reliability was calculated.
Results: The intraclass coefficient of reliability was 0.27 over all observations suggesting that about a quarter of total variance is due to between-subject variance. Taking means over each year increased reliability to 0.60. Linear regression analyses with ECP being the dependent variable demonstrated significant higher values for boys (beta=12.26; P < 0.01), children sensitized to seasonal (beta=34.27; P=0.02) but not to perennial allergens (beta=-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.