Description:
<jats:title>ABSTRACT</jats:title><jats:p>In asthma, clinical symptoms and lung function are insensitive in reflecting the underlying airway inflammation, and monitoring of this process has only recently become available. Fractional exhaled nitric oxide (F<jats:sc>e</jats:sc><jats:sub>NO</jats:sub>) is now recognized as a reliable surrogate marker of eosinophilic airway inflammation and offers the advantage of being completely non‐invasive and very easy to obtain. This review summarizes the clinical use of F<jats:sc>e</jats:sc><jats:sub>NO</jats:sub> in asthma. It covers the relationship between F<jats:sc>e</jats:sc><jats:sub>NO</jats:sub> and the underlying eosinophilic inflammation, the pathophysiology and production of F<jats:sc>e</jats:sc><jats:sub>NO</jats:sub>, technical aspects of F<jats:sc>e</jats:sc><jats:sub>NO</jats:sub> measurement and potential confounding factors in interpreting levels. F<jats:sc>e</jats:sc><jats:sub>NO</jats:sub> reference values and the role of F<jats:sc>e</jats:sc><jats:sub>NO</jats:sub> in asthma assessment, diagnosis and management are also discussed.</jats:p>