Induced sputum inflammatory measures correlate with lung function in children with cystic fibrosis

Objective: To validate a sputum induction technique in cystic fibrosis (CF), we examined the relation between airway inflammation and pulmonary function in children with CF by correlating inflammatory indexes in induced sputum with FEV1. Study design: We measured baseline spirometry and oxygen saturations and then performed sputum inductions with 3% hypertonic saline in 20 clinically stable children with CF (I I girls). We examined the relation of air-way inflammation and lung function in the 19 individuals (95%) who expectorated an adequate sputum sample. Measures of airway inflammation in induced sputum included total cell counts, neutrophil (PMN) counts, interleukin-8 levels, and free neutrophil elastase activity. Results: There were significant inverse relations between FEV1 and total cell counts and PMN counts (r = -0.57, P < .01 for both), interleukin-8 (r = -0.72, P = .002), and elastase (r = -0.75, P = .001). Airway infection, as assessed by bacterial density in induced sputum, did not correlate with lung function or indexes of inflammation. Conclusions: We conclude that measures of inflammation in induced sputum correlate with FEV1 in clinically stable children with OF with normal to mildly abnormal lung function and that they may be useful as surrogate outcome measures in clinical trials.