Exhaled nitric oxide concentration is affected by age, height, and race in healthy 9-to 12-year-old children

Background: The fractional concentration of exhaled nitric oxide (FENO) is a useful indicator of airway inflammation in children and adults with asthma. Methods: We determined the range of FENO concentrations and the factors affecting it in a large sample of healthy school children attending grades 4 through 6, in Windsor, ON, Canada. Results: FENO was measured in 657 children between 9.1 and 12.9 years of age. The range of FENO concentrations in healthy school children was 12.7 parts per billion (ppb) [95% confidence interval (0), 11.8 to 13.7 ppb] in whites and 22.8 ppb [95% CI, 17.9 to 27.7 ppb] in Asian-Canadian children (p < 0.001). FENO values also appeared to be higher in African-Canadian children than in whites, although the CI was wide because of the small number of African-Canadian children sampled. FENO rose slightly but significantly with age (p = 0.007) and with height (p = 0.023). Body mass index and gender did not significantly alter the measured FENO. FVC had a nonsignificant effect on FENO. Participation in physical activity during the same day had a borderline-significant effect on measured FENO, but a reported history of a respiratory tract infection in the preceding 2 weeks did not. Conclusions: FENO concentrations in healthy school-aged children appeared to be affected by race, and, to a lesser extent, by age and height. These factors should be taken into consideration when interpreting clinical results.