Induced sputum : whole sample.

With the introduction of fiberoptic bronchoscopy and the ability to carry out bronchoscopic biopsy and broncho-alveolar lavage (BAL) in patients and control subjects, characterisation of inflammation in airways diseases such as asthma and chronic obstructive respiratory disease (COPD) has been possible. This has allowed emphasis to be placed on the role of inflammation in diseases such as asthma (1) and COPD (2). Bronchoscopy, being an invasive procedure, carries an associated morbidity (3,4). Although bronchoscopy is carried out in patients with moderate or even severe airflow limitation for clinical indications, it is not ethically justified to carry out research bronchoscopies on such patients, as it is essential to pursue research procedures carrying the minimum risk to volunteer subjects. Thus BAL, for the purposes of research in airways diseases, is limited to patients with mild airflow obstruction, thus requiring extrapolation of findings to a more heterogeneous group of patients. As a consequence of its invasive nature, the number of times the procedure can be repeated is limited so that it may be difficult to study the kinetics of the inflammatory response. In addition, it may be difficult to recruit volunteers for studies that necessitate bronchoscopy.