Exhaled nitric oxide and respiratory symptoms in a community sample of school aged children.

Objective: To test the association between reported allergy and allergic diseases, respiratory symptoms, and the fractional concentration of exhaled nitric oxide (FeNO), in a community sample of school aged children.

Methodology: We administered a respiratory questionnaire and measured FeNO in a cross-sectional study of 1,135 children.

Results: FeNO was significantly greater in children with reported asthma (20.3 (standard deviation (SD) 21.3) parts per billion (ppb)) or allergies (18.1 (SD 18.0) ppb) than in healthy children (14.0 (SD 13.4) ppb). It was greater in children with asthma and reported allergies (22.8 (SD 23.6) ppb), than in children with asthma but no allergies (15.8 (SD 15.6) ppb) (overall P-value between disease groups = 0.002). FeNO was not related to respiratory symptoms in healthy children. Eczema was associated with an elevated FeNO concentration, even in the absence of respiratory symptoms. Some children with reported allergies but not asthma who had respiratory symptoms suggestive of asthma had elevated FeNO concentrations, and the proportion of healthy children with reported bronchitis or pneumonia in the past year who had an abnormally high FeNO concentration was significantly elevated.

Conclusions: In a community sample of children, FeNO concentrations appear to reflect allergic conditions, including allergic asthma, reported allergies, and eczema, rather than just asthma, particularly since asthma in children may be non-allergic. FeNO is similarly elevated in school aged children with reported asthma or reported allergies. FeNO is higher in children with asthma and allergies than in children with asthma alone. However, an elevated FeNO may help alert the clinician to the possibility of undiagnosed asthma.