Cellular composition of induced sputum in healthy adults

Abstract

Objective: To establish reference values for cellularity in induced sputum samples collected from healthy adults.

Methods: Induced sputum samples were obtained from 88 healthy adult never-smokers (39 males). The mean age was 36 years (range, 18-68 years). The participants had been residing in the city of Florianópolis, Brazil (a medium-sized non-industrial city) for at least two years. After the samples had been processed, we obtained total and differential cell counts.

Results: The mean total cell count was 4.8 ± 4.2 × 10(6) cells/g. There was a predominance of macrophages (mean, 77.5 ± 14.7%) and neutrophils (mean, 23.4 ± 14.3%). Eosinophils were virtually absent (mean, 0.1 ± 0.3%). Lymphocytes and bronchial epithelial cells were scarce. Neither age nor atopy had any effect on the total or differential cell counts.

Conclusions: In the induced sputum of this healthy adult population, macrophages and neutrophils predominated. However, the proportion of neutrophils was lower than that reported in previous studies, which suggests that reference values might vary depending on geographic location.