Changes in sputum composition during 15 min of sputum induction in healthy subjects and patients with asthma and chronic obstructive pulmonary disease

Summary Introduction The use of sputum induction by inhalation of hypertonic saline to study the cellular and biochemical composition of the airways allows noninvasive sampling of the airways content and identification of markers of airways inflammation. Objective The present study aimed to identify possible changes in the cellular composition of induced sputum between samples obtained sequentially (three periods of 5 min each) during one sputum induction. Moreover, difference between these samples and the mixed one (mixture of samples obtained after 5, 10 and 15 min of induction) was investigated. Methods Forty-six subjects (10 healthy volunteers, 12 patients with chronic obstructive pulmonary disease (COPD) and 24 patients with asthma) (mean age 53.0±14.0 yr, forced expiratory volume in one second (FEV1 ) 71.8±19.0% pred) produced sputum after three consecutive 5 min periods of hypertonic (4.5%) saline inhalation. Stained cytospins from the three periods separately and from the mixed sample were produced and analyzed. Results The mean percentage of neutrophils, eosinophils, lymphocytes and epithelial cells did not change significantly in samples obtained consecutively after 5, 10 and 15 min of the induction procedure. There was no significant difference in the cellular composition of samples obtained after 5, 10 and 15 min of induction and the cellular composition of the mixed sample ( P= 0.06). Conclusion The separate analysis of induced sputum from three consecutive sampling and the mixed sample did not demonstrate significant changes in their cellular composition. Fifteen minutes induction procedure with the fixed concentration of hypertonic saline and processing of the mixed sample can be recommended for clinical settings and clinical trials.