MEASUREMENT OF CD34-POSITIVE CELL COUNT BY THE PROCOUNT METHOD: COMPARISON WITH STANDARD FLOW CYTOMETRIC ASSAY

The ProCOUNT™ kit (Becton-Dickinson Immunocytometry Systems) has recently been developed for the measurement of CD34-positive cells. Here we describe a comparative study of CD34-positive cell counting by ProCOUNT™ and standard two-dimensional side scatter-fluorescence representation (SSC-FL) using nucleated cells from peripheral blood (PB: n=15) and cord blood (CB: n=20). A high correlation was found between the two methods: r=0.997, Y=0.991X+0.044 for the PB cells and r=0.944, Y=0.891X+0.02 for the CB cells. The percentages of CD 34-positive cells in the PB cells were 1.49% and 1.46% by the two methods, and both 0.25% in the CB cells. Further, a high correlation (r=0.945-0.960) between the percentage of CD34-positive cells and CFU-GM cell counts was also found in PB cells measured by these two methods. However, this correlation coefficient in CB cells by SSC-FL was 0.684, even though a high correlation (r=0.819) in the same CB cells was found by ProCOUNT™. This difference appears to be due to a higher percentage of non-hemolytic red blood cells in the SSC-FL (mean±1SD: 32.45±25.10%) than in the ProCOUNT™ (15.17±10.49%). As a consequence, we consider that ProCOUNT™ is preferable in the measurement of CD34-positive cell counts in PB and CB cells for standardization, especially in cord blood bank use.