COMPARISON BETWEEN HYPERTONIC AND ISOTONIC SALINE-INDUCED SPUTUM IN THE EVALUATION OF AIRWAY INFLAMMATION IN SUBJECTS WITH MODERATE ASTHMA

Background Hypertonic saline-induced sputum has recently been used for the evaluation of airway inflammation in asthma. Objective To assess the effect of hypertonicity on airway inflammation. Methods We compare d the inflammatory cell composition of hypertonic saline-induced sputu m with that of isotonic saline-induced sputum in 21 asthmatic subjects and, at baseline and 30 min after each sputum induction, we measured bronchial hyper-responsiveness to methacholine as an indirect marker t o detect increased airway inflammation. On two different days, the pat ients inhaled hypertonic saline (3-5% NaCl) or isotonic saline (0.9% N aCl) for 30 min via an ultrasonic nebulizer, while monitoring FEV(1). Sputum was collected for inflammatory cell analysis. Results There was no difference in inflammatory cell percentages obtained with the two methods. Eosinophils were >1% in 20 subjects after hypertonic saline a nd in 16 subjects after isotonic saline, but this difference was not s tatistically significant. Intraclass correlation coefficients for sput um inflammatory cells obtained with the two methods were +0.642 for eo sinophils, +0.644 for neutrophils, +0.544 for lymphocytes and +0.505 f or macrophages. Hypertonic saline induced bronchoconstriction in a sig nificantly greater number of subjects than isotonic saline. Also, hype rtonic saline increased bronchial responsiveness to methacholine, whil e isotonic saline did not. Conclusion We conclude that hypertonicity d oes not affect sputum cell composition, suggesting that inflammatory c ells in hypertonic saline-induced sputum are probably preexisting and not acutely recruited in the airways by the hypertonic stimulus. Howev er, the bronchoconstriction and the increase in bronchial hyper-respon siveness after hypertonic saline inhalation may imply the release of i nflammatory mediators. This fact must be considered in the evaluation of soluble markers of inflammation in hypertonic saline-induced sputum .