Use of exhaled nitric oxide in the diagnosis and monitoring of childhood asthma: myth or maxim?

Asthma is a common condition in children. This review describes the evidence from the literature and international asthma guidelines for using fractional exhaled nitric oxide (F_ENO) in the diagnosis and monitoring of childhood asthma. The accuracy of F_ENO measuring devices could be further improved, the difference in F_ENO results between devices are equivalent to what is considered a clinically important difference. For diagnosing asthma no guideline currently recommends F_ENO is used as the first test, but many recommend F_ENO as part of a series of tests. A cut-off of 35 ppb is widely recommended as being supportive of an asthma diagnosis, but evidence from children at risk of asthma suggests that a lower threshold of 25 ppb may be more appropriate. Nine randomised clinical trials including 1885 children have added F_ENO to usual asthma care and find that exacerbations are reduced when care is guided by F_ENO (OR for exacerbation compared to usual care 0.77, 95% CI 0.62-0.94). What is not clear is what cut-off(s) of F_ENO should be used to trigger a change in treatment. After 30 years of intensive research there is not sufficient evidence to recommend F_ENO for routine diagnosing and monitoring asthma in children.

Educational aims: To give the reader an overview of literature that supports and does not support the role of F_ENO in diagnosing asthma in children.To give the reader an overview of literature that supports and does not support the role of F_ENO in monitoring asthma in children.To give the reader an understanding of the role of F_ENO in international guidelines for diagnosing and monitoring asthma in children.