The development of standardized methods for sputum induction has improved the quality and reproducibility of sputum samples. This technique has been used to optimize samples in the investigation of
pulmonary tuberculosis and
lung cancer, but its clinical application as a noninvasive measure of airway
inflammation has highlighted the enormous potential of this technique. Sputum induction has allowed researchers to characterize the inflammatory profiles of a variety of airway diseases including
asthma,
COPD, and
chronic cough. To date, the identification of sputum
eosinophilia has the greatest clinical value as this predicts a favorable response to
corticosteroids and can therefore guide treatment. In
asthma and
COPD management, protocols aimed at normalizing the sputum eosinophil count have markedly reduced exacerbations without an overall increase in
therapy. Currently, no other noninvasive measure of airway
inflammation has demonstrated a benefit in reducing exacerbations. The value of sputum induction and analysis is not restricted to the recognition of sputum
eosinophilia but also may be used to direct novel antineutrophilic
therapies. Thus, it is time for sputum induction to move from the research laboratory to the clinic.