By how much can exhaled nitric oxide vary over three months in children with stable asthma?

Turner, Stephen, Fielding, Shona, Pijnenburg, Marielle, De Jongste, Johan, Pike, Katy, Roberts, Graham, Petsky, Helen, Chang, Anne, Fritsch, Maria, Frischer, Thomas, Gergen, Peter, Szefler, Stanley, Vermeulen, Francoise and Vael, Robin (2019) By how much can exhaled nitric oxide vary over three months in children with stable asthma? European Respiratory Journal, 54. (doi:10.1183/13993003.congress-2019.PA5419).

Abstract

Introduction: repeated measurements of fractional exhaled nitric oxide (FeNO) may be useful objective measurements in the management of asthma. There is uncertainty in what merits a clinically-relevant change in FeNO. Methods: individual participant data were obtained from seven randomised controlled trials where FeNO was used to guide asthma treatment. The FeNO values at the start and end of a period of stable asthma were analysed. The median absolute and percentage change in paired FeNO measurements at the start and end of a stable period were determined for individuals with a baseline FeNO of <50ppb and ≥50ppb, and also for ranges <11ppb, 11-20ppb, 21-30ppb, 31-40ppb and 41-49ppb. Results: data were available in 665 children (mean age 13.1, 59%male). When the initial FeNO was <50ppb (n=543), the median [IQR] absolute change in FeNO was +2ppb [-4, +9] and percent change in FeNO was +10 [-25, +66]. When stratified by different ranges of values <50ppb, the upper quartile values of absolute change in FeNO were +5ppb, +10ppb, +13ppb, +30ppb and +21ppb for <11ppb (n=165), 11-20ppb (n=162), 21-30ppb (n=100), 31-40ppb (n=66) and 41-49ppb (n=41) respectively. Where the initial FeNO was ≥50ppb (n=131), the median [IQR] absolute change in FeNO was -8ppb [-28, +18] and percent change in FeNO was -11 [-38, +32]. Conclusions: these findings support current recommendations for interpretation of what may be a clinically relevant change in a FeNO value of ≤20ppb but for higher values, greater absolute and percentage change in FeNO values should be tolerated before any alteration in treatment is considered.

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Contributors

Author: Graham Roberts

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