Airway inflammation in steroid-naïve asthmatics: characteristics of induced sputum

RESUMO

BACKGROUND: Airway inflammation, acknowledged as an important feature of asthma, can be assessed by the examination of induced sputum. OBJECTIVE: To determine the pattern of inflammatory cells in induced sputum from stable steroid-naïve asthmatics, in Florianópolis, Santa Catarina. METHOD: The induced sputum from 34 asthmatics using exclusively inhaled bronchodilators on demand was examined. The patients' clinical characteristics were obtained at visit 1, and sputum was induced at visit 2. Differential cell count was performed on Giemsa-stained cytospins. Sputum was considered to be eosinophilic if there were 3 percent eosinophils, and neutrophilic if there were 65 percent neutrophils. RESULTS: Results are expressed by median and interquartile range. The total cell count was 3.4 (3.7) x 10(6) cells/ml, and cell viability was 80.0 (16.4) percent. The proportion of neutrophils was 14.4 (22.1) percent, of eosinophils 6.4 (17.2) percent, of macrophages 60.3 (37.5) percent, and of lymphocytes 1.1 (1.2) percent. Eosinophilic sputum was observed in 24 subjects (70.6 percent); none of them had neutrophilic sputum. There were no significant differences between the eosinophilic and non-eosinophilic groups concerning the measured clinical outcomes, total cell count and proportions of cells in the sputum, except for the proportion of eosinophils (14.4 [19.3] vs 0.4 [1.1], p < 0.001). CONCLUSIONS: In our environment, steroid-naïve asthmatics present a higher proportion of sputum eosinophils, as compared to the established reference values. The clinical and physiological parameters analyzed were unable to predict the presence of eosinophilic inflammation of the airways.