The cellular composition of induced sputum in chronic obstructive pulmonary disease

Asthma and chronic obstructive pulmonary disease are characterized by airwa y inflammation, which can be assessed by bronchoscopic techniques as well a s by the analysis of induced sputum. A method to induce sputum with inhaled hypertonic saline was adapted for us e in 21 chronic obstructive pulmonary disease (COPD) patients (mean baselin e forced expiratory volume in one second (FEV1) 1.60 L, or 54% predicted) a nd in 16 healthy volunteers. The success rate and safety of the method, wer e investigated along with the reproducibility of cell counts and difference s in cell counts between both groups. All subjects produced adequate samples and the procedure did not alter spir ometric values. A marked sputum neutrophilia was noted in patients with COP D (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 invest igators (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 macrop hages 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 obs tructive pulmonary disease.