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Exhaled Nitric Oxide Concentration Is Affected by Age, Height, and Race in Healthy 9- to 12-Year-Old Children^*

^* From the Department of Pediatrics (Dr. Kovesi), Children’s Hospital of Eastern Ontario, University of Ottawa, Ottawa, ON, Canada; and the Air Health Effects Division (Mr. Kulka), and the Biostatistics and Epidemiology Division (Dr. Dales), Health Canada, Ottawa, ON, Canada.

Correspondence to: Thomas Kovesi, MD, Department of Pediatrics, Children’s Hospital of Eastern Ontario, 401 Smyth Rd, Ottawa, ON, Canada K1H 8L1; e-mail: kovesi{at}cheo.on.ca

Abstract

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 (CI), 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.

Key Words: Asian continental ancestry group • asthma • breath tests • child • continental population groups • growth • nitric oxide • reference values