The evaluation of a cell dispersion method of sputum examination

In recent studies, sputum smear cell counts were found to be reproducible and usefully applied to research in asthma and other airway conditions. However, cell definition on the smears is poor, and the procedure is tedious and has limited utility. The objective of this study is to improve the methods of sputum examination. The subjects used in this study were people with bronchitis or asthma from whom sputum could be obtained. By inverted microscopy, portions of fresh sputum were selected to exclude salivary contamination. These portions were exposed to different volumes of dithiothreitol for varied time intervals. We used the resulting cell suspensions to perform total cell counts and prepare cytospins for differential cell counts and immunohistochemical stains for GM-CSF, EG2, TNF alpha and IL-8. Cytospins were compared with smears for differential cell counts on the same sputum specimens. Excellent cell dispersion and definition in cytospins could be observed. The time required for differential cell counting on cytospins was reduced and cytospin counts were more reproducible than smears. Greater duration of treatment of sputum with dithiothreitol tended to increase total cell counts and significantly decreased EG2 staining but had no effect on differential cell counts or the cytokine cell components. Therefore the proposed method of sputum examination involving cell dispersion and use of cytospins overcomes a number of the disadvantages of the examination of smears.