Measurement of FeNO in asthma: what the hospital doctor needs to know.

Asthma is the commonest chronic lung disease. Airway inflammation is a central component of asthma but clinical symptoms of asthma and standard spirometry are insensitive in reflecting the underlying inflammatory processes. Measurement of the fractional nitric oxide concentration in exhaled breath (FeNO) is a quantitative, non-invasive and safe method of measuring airway inflammation. Advances in technology and standardization have made FeNO measurements simple, enabling their use as a biomarker alongside traditional clinical tools in the assessment and management of asthma. Specifically, it can predict responsiveness to steroids and also newer biological therapy, predict future risk of exacerbation and help highlight treatment non-adherence, making it a useful asset to personalized medicine.