An increase of <50% in fractional exhaled nitric oxide (FeNO) during a 3-month period is unlikely to be clinically meaningful in children with asthma, according to the results of a study published in Pediatric Pulmonology.

Researchers used clinical data from 7 clinical trials that included FeNO measurements obtained from children with asthma. Both absolute and percentage change FeNO measurements during stable and unstable 3-month periods were examined to determine what percentage increase was likely to be clinically meaningful. Stable periods were defined as 2 successive assessments during the course of 3 months with controlled asthma, where the dose of inhaled corticosteroids remained unchanged and there was no exacerbation requiring oral corticosteroid treatment.

A total of 1112 participants were analyzed, 665 of whom had ≥1 stable period. For all stable participants combined, the mean percentage change was +26%. In addition, there were 48 individuals identified who experienced consecutive periods of stable asthma followed by unstable asthma. There were no differences in change in FeNO between the stable and unstable periods.

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The researchers noted that these results may be relevant to clinicians when interpreting repeated FeNO measurements, particularly when making treatment decisions for a child already diagnosed with asthma.


Fielding S, Pijnenburg M, de Jongste J, et al. What is a clinically meaningful change in exhaled nitric oxide for children with asthma? [published January 7, 2020]. Pediatr Pulmonol. doi:10.1002/ppul.24630