Analysis of induced sputum: a new approach to the study of airway inflammation in asthma.

Induced sputum is a simple method that enables the analysis of lower respiratory tract material obtained through non-invasive methods. Validation of the technique for the study of airway inflammation in asthma and other respiratory diseases, together with the most relevant findings reported in the literature, are reviewed herein. Accurate methods that can be applied to the analysis of induced sputum samples, such as immunocytochemistry, flow cytometry or polymerase chain reaction are also discussed.