Differential cytology of bronchoalveolar lavage fluid in normal children.

Bronchoalveolar lavage (BAL) is increasingly used in the assessment of pulmonary diseases in children. However, reference values for cellular and non-cellular constituents of BAL fluid in children are lacking. We have studied the differential cytology of BAL fluid in 48 children aged 3-16 years (mean age +/- SD 7.9 +/- 3.5 yrs) undergoing elective surgery for nonpulmonary illnesses. A flexible bronchoscope (Pentax 3.5 or 4.9 mm) was wedged in the middle lobe or one of its segments. BAL was performed with 3x1 ml-kg-1 body weight of normal saline warmed to body temperature. The first sample was studied separately; subsequent samples were pooled for analysis. The mean recovery was 58 +/- 15%. Significantly more granulocytes and less lymphocytes were found in the first, as compared to the pooled, sample. Total cell counts were highly variable and ranged from 0.5-57.1 x 10(4) ml-1. Macrophages were the predominant cell type, with a mean percentage of 81.2 +/- 12.7%. The relative proportion of lymphocytes was higher than that reported in most studies of adult volunteers (16.1 +/- 2.4%). No age dependency was observed for either cell type. The mean percentage of granulocytes was 2.5 +/- 3.3%. Absolute granulocyte counts were significantly higher in children under 8 yrs of age. This study provides the first reference data on BAL differential cytology in children without pulmonary disease and will be the basis for future investigations of BAL in paediatric lung diseases.