Reference Values And Influence Factors Of Fractional Exhaled Nitric Oxide For Healthy Children In Soochow

Objective: The aim of this study was to establish FeNO reference values for healthy school-age children in Soochow according to the international guidelines, and to assess the determinants of FeNO in healthy children.Methods: 450 school children age range 6 ~14 years were recruited from two public schools in Soochow. The subjects were examined with regard to measurement of FeNO, spirometry, anthropometric variables, and blood eosinophil, and completed a respiratory questionnaire. FeNO was measured online by a chemiluminescence analyzer according to ATS/ ERS standard. The associations between different determinants and FeNO were analyzed with stepwise multiple regression analysis.Results: Among the subjects, 225 children fulfilled the criteria of healthy subjects (107 boys, 118 girls).The Geometric mean of FeNO in 225 children was 10.8 parts per billion (ppb) (95% confidence interval C.I., 4.2~27.5 ppb). No difference was found between boys (mean value, 11.1ppb; 95% C.I., 4.0~30.7 ppb) and girls (mean value, 10.5 ppb; 95% C.I., 4.5~24.8 ppb) (T=0.864, P=0.389). In the random sample of children, EOS% was found to be the best independent variable for the regression equation for FeNO, which on average showed an increase in the EOS% range of 0.2%~3.9% from 9 to 20 ppb (r=0.3, P<0.0001). Height was the second independent variable for the regression equation for FeNO, which on average showed an increase in the height range of 116~176 cm from 10 to 15 ppb (r=0.1, P=0.027). There was an insignificant correlation between FEV1 and FeNO (r=0.1, P=0.038). No correlation was found between age, weight, BMI, FEV1/FVC% and FeNO levels. The achievement ratio of measurement of FeNO was 99.2%. Conclusion: This study establishes a reference range for FeNO values measured by NIOX in children age range 6~14 years. Based on the results, it suggests that the values for healthy children should be considered to fall between the following ranges: 4~27 ppb. FeNO levels in healthy children are dependent of EOS% and height significantly, and independent of age, gender, BMI and FEV1/FVC%, and have an insignificant correlation with FEV1. Measurement of FeNO by NIOX is simple, safe and feasible in school-age children. It can be used to monitor airway inflammation in asthmatic children.