Induced sputum in children: success determinants, safety, and cell profiles

Sputum induction is a noninvasive method for the assessment of airway inflammation.

To evaluate the safety of the procedure and the clinical predictors of successful induction, and to analyze the relationship between sputum cell counts and clinical features in asthmatic and nonasthmatic children.

We reviewed sputum inductions performed in our department between 2006 and 2008 in individuals under 18 years; 34 asthmatic and 24 nonasthmatic children were included. Sputum induction was performed with 4.5% saline for 5-minute periods with salbutamol pretreatment. The most viscid portions were selected for processing. Inductions which were tolerated for less than 4 minutes or which produced a sample volume of less than 1 mL or a sample with a squamous cell percentage of over 80% were considered unsuccessful.

Sputum induction was successful in 43 (74%) of the 58 children studied.The total median induction time was 15 minutes (interquartile range, 10-15 minutes). Only 7 individuals (12%) experienced mild symptoms, which were easily reversed with salbutamol inhalation in all cases. The mean (SD) overall PEF variation with induction was -2.5% (7%), with no significant differences between asthmatics and nonasthmatics. Asthmatics had significantly higher total cell counts (P = .007), macrophages (P = .033), and relatively fewer neutrophils (P = .003) than nonasthmatics; metachromatic cells were rare and seen only in asthmatics (P = .026). We found a positive correlation between exhaled nitric oxide and sputum eosinophil count (r = 0.363, P = .017).

Sputum induction is a safe, noninvasive, and feasible procedure that allows the direct assessment of airway inflammation in most children.