Non-invasive assessment of airway inflammation

This chapter reviews the methodology and validation of induced sputum and FENO and outlines other more experimental approaches to the assessment of airway inflammation. There has been an explosion of interest in the assessment of airway inflammation using non-invasive means and there are now a large number of different techniques to assess airway inflammation, each with its own strengths and weaknesses. Two techniques are particularly well developed and are already widely used in clinical trials and impacting on clinical practice: induced sputum, where a sputum differential and total cell count is used to determine the characteristics and intensity of the lower airway inflammatory response; and exhaled nitric oxide (FENO), where the concentration of nitric oxide (NO) in exhaled air is used to provide information about the presence of eosinophilic, corticosteroid responsive airway inflammation. The different strengths and weaknesses of the techniques suggests that they may find different roles, with FENO being used mainly in primary care to facilitate diagnosis and to titrate corticosteroid therapy and induced sputum used in secondary and tertiary care, where more detailed information on the type of lower airway inflammation is necessary. The chapter finishes by discussing how the widespread application of induced sputum to large and heterogeneous populations of patients with airway disease has furthered our understanding of the complex relationship between airway inflammation and the clinical expression of airway disease and opened the way to a new approach to the management of airway disease based on assessment of airway inflammation. © 2009 Elsevier Ltd All rights reserved