The Interpretation of Exhaled Nitric Oxide Values in Children With Asthma Depends on the Degree of Bronchoconstriction and the Levels of Asthma Severity

BACKGROUND: The clinical implications of fractional exhaled nitric oxide (F ENO ) measurements in childhood asthma are unclear. We aimed to evaluate the relationship between the level of exhaled nitric oxide and pre-bronchodilator FEV 1 and the change in FEV 1 after bronchodilator in children with asthma. METHODS: This was a retrospective, cross-sectional study. We evaluated data from medical documentation of children with asthma with special attention to F ENO results, asthma severity, FEV 1 (% predicted), and bronchial reversibility test. RESULTS: Four hundred and five subjects (age 6–18 y) completed the study. Median levels of F ENO increased linearly with subjects' age ( P = .03). We found a nonlinear trend of pre-bronchodilator FEV 1 across 4 quartiles of F ENO in episodic and mild asthma; we observed lower pre-bronchodilator FEV 1 in children with higher F ENO , but only up to the F ENO value of 35.4 ppb; in children with F ENO value > 35.4 ppb, pre-bronchodilator FEV 1 was increased. We found a linear increasing trend of change from baseline (after 400 μg of salbutamol) in FEV 1 across F ENO categories in children with moderate asthma. CONCLUSIONS: Our results suggest a need to measure F ENO before as well as after spirometry. Consequently, in children with asthma with bronchial obstruction, we suggest assessing F ENO after short-acting β 2 agonists as well. (ClinicalTrials.gov registration NCT00815984.)