Bone marrow cell differential counts obtained by multidimensional flow cytometry.

Five-dimensional flow cytometric analysis of normal bone marrow aspirates was utilized to determine the frequency of neutrophils, eosinophils, monocytes, lymphocytes, nucleated erythrocytes, reticulocytes, platelets, and a cell population that included blasts of each of the cell lineages, megakaryocytes, plasma cells, and basophils. Each of these bone marrow cell populations had unique features with respect to forward light scatter, orthogonal light scatter, and staining with Thiazole-Orange, LDS-751, and CD45 labeled with Phycoerythrin (PE). The identity of the cell populations was verified by sorting each of the cell populations and subsequent light microscopic examination of the cells. The frequencies of the nucleated bone marrow cell subpopulations of 50 normal donors were for neutrophils, mean 72.3%; SD +/- 5.1; 95% limits, 70.9-73.8%; eosinophils, mean 1.8%; SD +/- 1.3; 95% limits, 1.4-2.1%; monocytes, mean, 2.8%; SD +/- 1.2; 95% limits, 2.5-3.1%; lymphocytes, mean 12.1%; SD +/- 3.6; 95% limits 11.1-13.2%; nucleated erythrocytes, mean 8.9%; SD +/- 3.9; 95% limits, 7.8-10.1%; and the cell population that included blasts of each of the cell lineages, megakaryocytes, plasma cells, and basophils, mean 1.6%; SD +/- 1.2; 95% limits, 1.3-1.9%. The percentage of reticulocytes in bone marrow aspirates from 50 normal donors correlated with the reticulocyte frequency in the peripheral blood of these donors. However, the mean frequency of reticulocytes was significantly greater (p < 0.0001) in bone marrow (mean 2.19%; SD +/- 0.88) than in peripheral blood (mean 1.71%; SD +/- 0.88). The technique could discriminate between immature and mature reticulocytes based on the brighter staining with both Thiazole-Orange and LDS-751 of the immature reticulocytes. This was confirmed by cell sorting of both reticulocyte populations, which revealed larger clumps of New Methylene Blue staining material in the brighter Thiazole-Orange and LDS-751 stained reticulocytes. The immature reticulocytes were present in normal bone marrow, but not in normal peripheral blood. As expected, a significantly greater frequency of nucleated cells was found in bone marrow aspirates (mean 0.85%; SD +/- 0.59) than in peripheral blood (mean 0.20%; SD +/- 0.11). The frequency of platelets was significantly lower in bone marrow (mean 1.24%; SD +/- 0.69) than in peripheral blood (mean 2.94%, SD +/- 1.14). Flow cytometric bone marrow analysis can provide clinical laboratories with a technique that generates quantitative bone marrow cell differentials and potentially can reduce the need for light microscopic examination of bone marrow smears.