Search

Asthma and chronic obstructive pulmonary disease are characterized by airway inflammation, which can be assessed by bronchoscopic techniques as well as by the analysis of induced sputum. A method to induce sputum with inhaled hypertonic saline was adapted for use in 21 chronic obstructive pulmonary disease (COPD) patients (mean baseline forced expiratory volume in one second (FEV1) 1.60 L, or 54% predicted) and in 16 healthy volunteers. The success rate and safety of the method, were investigated along with the reproducibility of cell counts and differences in cell counts between both groups. All subjects produced adequate samples and the procedure did not alter spirometric values. A marked sputum neutrophilia was noted in patients with COPD (74.9+/-4.7%), whereas mainly macrophages were seen in healthy volunteers (74.0+/-4.0%). Reliability of the cell counts was high, both within investigators (r=0.99 neutrophils, r=0.99 macrophages) and between investigators (r=0.95 neutrophils, r=0.77 macrophages). In patients with COPD, an inverse correlation was noted between percentage of neutrophils and FEV1 (r(s)=-0.48, p<0.05). Immunostaining revealed a large proportion of activated macrophages in both groups. It was concluded that induction of sputum is a safe and reproducible method to study the composition of airway secretions in patients with chronic obstructive pulmonary disease.

Analysis of induced sputum has been proposed as a direct, relatively noninvasive method for the evaluation of airway inflammation in diseases such as asthma or chronic obstructive pulmonary disease (COPD). An important question in the validation of this technique concerns the potential influence of differences in the methods of examining sputum. Up to the present time, two basic techniques for processing sputum have been described. The first approach consists of selecting all viscid portions from the expectorated sample, whereas the second approach processes the whole expectorate, containing sputum plus saliva. Both processing techniques have been shown to provide valid and reliable data on the composition of the cellular and soluble fraction of induced sputum. From the data currently available, it would therefore appear that the usefulness of induced sputum as a method for assessing airway inflammation is not influenced by differences in the methods currently used for examining sputum.