Usefulness of diurnal variation of fractional exhaled nitric oxide for predicting early therapeutic response to asthma treatment

Abstract

Objective

Fractional exhaled nitric oxide (FeNO) is considered to be an adjunct for asthma management, although its usefulness remains controversial. Therefore, it may be necessary for new approaches to use FeNO for asthma management. We evaluated whether diurnal variations of FeNO can predict response to asthma treatment.

Methods

This pilot study consisted of 22 uncontrolled asthmatics and 16 healthy subjects. FeNO and peak expiratory flow (PEF) were measured by themselves twice daily at home for three weeks (asthmatics) or two weeks (healthy subjects), and daily mean and diurnal variations of FeNO and PEF levels were calculated. In uncontrolled asthmatics, treatment was intensified a week after study entry, and then control status was reevaluated after three to four weeks. Asthmatics were then divided into two groups; good or poor responders.

Results

Diurnal variations of FeNO levels, as well as daily mean FeNO and PEF levels, in uncontrolled asthmatics before intensive treatment were significantly higher than those in healthy subjects, regardless of treatment response (p < 0.01). Furthermore, in the good responders, diurnal variations of FeNO levels were significantly decreased in the 1^st week (p < 0.05) of intensive treatment, whereas the daily mean FeNO levels significantly dropped in the 2^nd week (p < 0.05). In the poor responders, no such changes were observed in FeNO levels. In terms of PEF, only the daily mean levels were significantly elevated after the initiation of intensive treatment, regardless of treatment response.

Conclusions

Diurnal variations of FeNO may contribute to predicting early therapeutic response to asthma treatment.

Keywords:

• Asthma
• fractional exhaled nitric oxide
• home monitoring
• diurnal variation
• therapeutic response

Acknowledgements

We thank Bedfont Scientific Ltd (Rochester, UK) for allowing us to use their portable analyzer (NObreath) to record FeNO levels. We would also like to thank the Scientific English Editing Section of Fukushima Medical University for their linguistic assistance in proofreading the manuscript.

Declaration of interest

MU received grants from JSPS KAKENHI. None of the rest of the authors received grants related with submitted work, and have no relevant conflicts of interests.

Author contributions

MU and JS contributed equally to this work. MU recruited patients, analyzed and interpreted the data, and drafted the manuscript. JS conceived and designed the study, recruited patients, analyzed and interpreted the data, and drafted and edited the manuscript. SS, AF, YSu, MR, TO, HT, NW, MS, JM, TKa, TU, RT, YS, TKo, KH, HM, TN, KK, and YT recruited patients, and interpreted the data. MM and YSh interpreted the data, and critically revised the manuscript. All authors approved the final version of the manuscript.

Funding

This study was partly supported by the JSPS KAKENHI grant (17K16054).