In a recent study, fractional exhaled nitric oxide (FeNO), a practical biomarker, was valuable in identifying and treating eosinophilic airway inflammation in chronic cough, potentially aiding in corticosteroid treatment decisions. The objective of the study was to scrutinize the literature to examine if FeNO serves as a modifiable trait in chronic cough, particularly in relation to other type 2 biomarkers. Additionally, the goal was to identify significant gaps in knowledge related to its clinical applications.

During the course of this narrative review, a thorough electronic search was performed on English-language literature using databases such as Web of Science, PubMed, and Scopus. The search utilized keywords including cough, nitric oxide, biomarker, treatable trait, and eosinophils.

The results of this investigation indicated that eosinophilic or type 2 airway inflammation has ameliorative potential in patients dealing with chronic cough. While induced sputum tests are acknowledged as the standard for defining the inflammatory phenotype, their technical complexity restricts widespread clinical use. On the other hand, FeNO, identified as a convenient biomarker, has emerged as a substitute for induced sputum assessment. Both mechanistic and clinical evidence suggest that FeNO holds the potential for diagnostic accuracy and predictability of treatment responses.