Abstract

Induced sputum with inhalation of saline solution is a non-invasive method used to collect material from lower airways. The standardisation of this method has improved the quality and reproducibility of sputum samples. An important advantage of the technique is that it enables sampling of the airways in patients with severe asthma and/or during exacerbation, under the appropriate conditions. For research purposes, it can be used in many patients and serial evaluations can be done. However, it is time consuming and requires experience. In patients with asthma, analysis of induced sputum has been investigated for studying airway inflammation, managing therapy, categorization of exacerbations, and diagnosis of occupational asthma. A significant reduction in asthma exacerbations has been shown in severe asthma patients with a treatment strategy based on suppressing sputum eosinophilia. It would be useful to increase the availability of the induced sputum technique, especially in tertiary clinics and in patients with severe asthma with frequent exacerbations. Induced sputum, bronchial biopsy, bronchoalveolar lavage, and exhaled NO are thought to sample from different compartments of the lung. Therefore, these methods are complementary and the research technique used depends on the purposes of the study.