Moreover the quality of the cytospins is better in the selected portion, principally because of less salivary contamination. Dithiothrietol, a mucolytic agent, is used to disperse the cells and liquefy the sample. Rocking and filtering help to obtain an homogenous sample. PCR techniques can detect mRNA expression of different markers in the cells. Measurements in disease Induced sputum seems to be a valid method to assess the airway inflammation in asthma.
Cell counts are highly reproducible and normal values of cell counts have been established.
Changes are more marked in induced sputum than in broncho-alveolar lavages. Sputum cell and fluid phase indices of inflammation are responsive to changes as indicat e d by increase in eosinophils, mast cells, tryptase and ECP after allergen challenges and decrease after treatmentwith inhaled or oral corticosteroids. Use of induced sputum has been already useful to understand certain mechanisms of asthma. Eosinophils and metachromatic cells are only weekly associated with bronchial hyperresponsiveness to methacholine but to be closely associated with changes in airway hyperresponsiveness after allergen challenge. Exacerbations of asthma induced by tapering the dose of i n haled steroids are associated with increased eosinophilic inflammation, whereas wild exacerbations of asthma are sometimes associated with neutrophilic inflammation.