Sputum induction: a method to assess airway inflammation in asthma.

Abstract
In recent studies, sputum cell counts have been used to examine the cell and molecular markers of airway inflammation. In this paper, we describe three different technical methods of analysing sputum samples: the first using smears, the second using cytocentrifugation after selection of a mucous plug, and the third using cytocentrifugation to analyse the entire sputum sample. These last two techniques have been used in a pilot study to compare the differential cell counts in sputum and bronchoalveolar lavage (BAL). The results show a significant correlation between the percentage of the eosinophils in sputum and bronchial sample of the BAL. Previous results on the study of airway inflammation with the analysis of sputum and the preliminary data on the relationship between sputum and BAL confirm the usefulness of this noninvasive technique in the understanding of the pathogenesis of asthma.