CD 45 gating correlates with bone marrow differential

In this study we assess a flow cytometric gating method and its correlation with a concurrent manual bone marrow differential in abnormal marrows. Like normal bone marrow cells, leukemic blasts fall into discrete areas when a cytogram of CD 45 expression and Right Angle Light Scatter is plotted in Log scale. We studied 50 specimens with a suspected diagnosis of leukemia. Gates were set on the eight discrete clusters typically found in normal bone marrow. We employed these gates to determine the differential of the abnormal bone marrows. Our results show a high correlation between the flow differential and the manual differential with the following r values: blasts 0.875; promyelocytes 0.914; myeloid precursors 0.879; neutrophils 0.776; lymphocytes 0.707; monocytes 0.913; and erythroid precursors 0.873. In addition some leukemic infiltrates appear to produce a characteristic pattern with the CD 45 vs. RALS cytogram. In this study, there is a total of 6 cases (3 false positives and 3 false negatives) where the flow differential does not render the same diagnosis as the manual differential, and 4 cases in which there is evidence of marked peripheral contamination leading to disagreement between the two methods. This method provides a relatively easy and powerful tool which can be applied to all bone marrow specimens that undergo flow cytometric analysis. It can greatly enhance the identification and lineage assessment of leukemic blasts in the bone marrow. The correlation with a manual differential is high, and this gating method may provide an inexpensive and easy means of obtaining an automated bone marrow differential.