[Induced sputum in children and adolescents with asthma: safety, clinical applicability and inflammatory cells aspects in stable patients and during exacerbation].

OBJECTIVES To determine the safety of sputum induction in asthmatic children and adolescents, to characterize sputum inflammatory cells while clinically stable and during exacerbation and to correlate sputum inflammatory cells with peripheral blood eosinophils, serum IgE and the degree of bronchial obstruction. METHODS Ninety-six asthmatic patients aged 6 to 18 years were recruited for the present cross-sectional study. Spirometry was performed before and after administration of a bronchodilator. Sputum was collected spontaneously or after induction by the inhalation of saline solution at increasing concentrations. Blood samples were obtained for serum IgE and eosinophil quantification. RESULTS Sputum samples adequate for analysis were obtained from 68 (70.8%) of the patients recruited. No relevant bronchoconstriction was observed during induction. The presence of a larger number of eosinophils in sputum did not correlate with more clinically severe asthma. No correlation was observed between the degree of bronchial obstruction, measured based on FEV1, and inflammatory cells in sputum, peripheral blood eosinophils or serum IgE. Larger numbers of neutrophils were observed in the asthma exacerbation group (p < 0.05). CONCLUSIONS Sputum induction was found to be a safe procedure for obtaining clinical samples from children and adolescents even during exacerbations, allowing for clinical and functional limitations. The 67% induction success rate was considered satisfactory. In this group of patients, receiving inhaled corticosteroids, eosinophil quantification did not distinguish between the clinical and functional severity of asthma and was independent of the degree of airway obstruction. A proportional predominance of neutrophils was observed in the sputum of patients with asthma exacerbation.