[Analysis of differential cell counts of sputa induced by inhalation of ultrasonically nebulized hypertonic saline or distilled water in asthmatic patients].

Bronchial asthma is an inflammatory disease of the airways, and a simple method of evaluating inflammation, safer than BALF or bronchial mucosal biopsy, has long been sought after. The induction of sputa by the inhalation of an appropriate solution and the examination of the induced sputa may provide such a method. We compared the safety of two sputum induction methods, ultrasonically nebulized hypertonic saline inhalation and distilled water inhalation, and examined the usefulness of differential cell counts of the induced sputa. The safety of these methods was ascertained by determining lung functions (FEV1.0, PEFR) and urinary leukotriene E4 before and after inhalation of these solutions, and the usefulness of differential cell counts of induced sputa by examining the uniformity/reproducibility. Only after the inhalation of distilled water did the lung function reveal a statistically significant decrease when the data were compared with the control values for each of the two methods (p < 0.01), and when the data obtained with distilled water inhalation and hypertonic saline inhalation were compared (p < 0.05). The urinary leukotriene E4 levels obtained were not very different between the two methods; however, in two patients, urinary leukotriene E4 levels were increased markedly only after inhalation of distilled water. The uniformity of the sputum differential cell counts in the same specimen (evaluated by intraclass correlation coefficient) and inter-specimens (evaluated by Friedman test) was satisfactory for both methods, except for basophils. Hypertonic saline inhalation at 24-hour intervals gave a better reproducibility in differential cell counts of the induced sputa (evaluated by interclass correlation coefficient), when compared with distilled water inhalation. These results suggest that hypertonic saline inhalation is safer and more useful than distilled water inhalation for induction of sputum in a uniform and reproducible way, and that the induction of sputum by hypertonic saline inhalation will be clinically useful in asthmatic patients who cannot expectorate sputa spontaneously.