Advanced Diagnostic Studies: Exhaled Breath and Sputum Analyses

Aim: The present paper aims to review the advantages and limitations of sputum cell counts and exhaled nitric oxide (FeNO) levels in the investigation of occupational asthma (OA). Methods: The American College of Chest physicians held a course on occupational and Environmental Lung Diseases in Toronto in 2013. A summary of the session on non-invasive measures of airway inflammation in OA is presented here. Results: Occupational asthma is associated with an increase in sputum eosinophil percentage during periods at work or after positive specific inhalation challenges. Changes in FeNO are less sensitive than sputum eosinophil counts for predicting OA. Conclusions: In settings where this tool is available, sputum eosinophil counts may complement the current investigation of OA. The interpretation of FeNO remains sometimes difficult. The phenotypes of patients who may benefit from this measure needs to be better defined.