Exhaled nitric oxide is reduced after sputum induction in asthmatic children

Exhaled nitric oxide (ENO) and eosinophil sputum markers are considered noninvasive markers of airway inflammation in asthma. The aim of this study was to evaluate whether the procedure of sputum induction can affect the level of ENO. We measured ENO before and after sputum induction by inhalation of hypertonic saline solution in 22 asthmatic children and 9 healthy controls. The ENO mean (+/- S. E.M.) value in the group of asthmatic children was reduced from a baseline value of 20.8 (+/- 3.0) ppb to 17.4 (+/- 2.4) ppb after sputum induction (P = 0.0012). In the healthy controls, the mean baseline value of ENO was 9.1 (+/- 2.1) ppb and it was reduced to 4. 8 (+/- 1.1) ppb after induction of sputum (P < 0.01). We suggest that measurements of ENO should be performed after the induction of sputum in asthmatic patients whenever both tests are done in sequence.