Airway inflammation in children with cystic fibrosis and healthy children assessed by sputum induction

Abstract

A noninvasive method to characterize inflammation and infection in the airways of nonexpectorating children with cystic fibrosis (CF) is needed for clinical and research purposes. Accordingly, we performed sputum inductions by administering 3% saline to 11 healthy control children and 20 children with CF, composed of 7 sputum producers (capable of spontaneously expectorating sputum) and 13 nonproducers. Induced sputum weights were comparable in each group, whereas the amount of induced sputum collected from the CF producers was over 10-fold higher than the spontaneously expectorated samples. We found a significant increase in indices of airway inflammation, including total cell counts, absolute neutrophil counts, interleukin-8 (IL-8) levels, and neutrophil elastase activity in the CF subjects compared with the healthy control subjects. These same indices in the induced sputum specimens from CF producers were significantly correlated with levels in the matched expectorated sputum specimens. Sputum total protein concentration was elevated in the CF groups, whereas urea and albumin levels were not significantly different. Salivary analysis, performed separately, revealed higher levels of IL-8 and total protein in the CF groups. Airway infection, as assessed by quantitative counts of CF-related bacterial pathogens, was also higher in the CF subjects. The same bacterial pathogens, in similar colony counts, were isolated from both the induced and expectorated sputum samples from the CF producers. We conclude that airway inflammation and infection, assessed through sputum induction, are significantly increased in children with CF as compared with healthy children. Furthermore, induced sputum samples are similar to spontaneously expectorated samples in describing both inflammation and infection in the CF airway.