EVALUATION OF THE FLOW CYTOMETRIC PARAMETERS MEASURING CD34+ CELLS IN CORD BLOOD 68

This study was scheduled to evaluate the different flow cytometric parameters used for the measurement of the absolute number of CD34+ cells in cord blood (CB). In samples of 86 CB units, the following parameters were determined by the use of the Coulter-XL flow cytometer: [a] total CD34+ cells,[b] low side scatter, bright fluorescence CD34+ cells (CD34++), [c] CD34+/CD45- cells. The percentage of the above CD34+ cells was determined both among the total cell population and the CD45+ white blood cells. The absolute number of CD34+ cells was determined on the cell concentration in each CB unit, as it was measured by the hematologic analyzer Cell-Dyn 3500 (Abbott), both in WIC (white cell impedence count) and WOCR (white cell optical countlysis resistant) channels. The analysis of the results indicated that:[a] The absolute number of CD34++ cells (83 +/- 56×10⁶) and CD34+/CD45- cells (95 +/- 77×10⁶), which commonly correspond to the stem cells, is significantly (p<0.05) lower than the absolute number of total CD34+ cells (779 +/- 782×10⁶), they do not differ significantly (paired-t-test, p=1.97) but show a strong positive correlation(r=0.951) between each other. [b] The linear regression between the absolute number of CD34+ cells and the white blood cells, measured by both the WIC and WOCR channels, appears with significant differences, as following: A strong regression was observed between the white blood cells and the total CD34+ cells (r=0.553, p=3×10^-9), while the regression between the white blood cells and the CD34++ cells was found less strong (r=0.332, p=0.001), and that between the white blood cells and the CD34+/CD45- cells appeared weak(r=0.178, p=0.1). It is concluded that: [a] Concerning the measurement of the absolute number of CD34+ cells in CB, CD34++ counts are equivalent to those of CD34+/CD45-. [b] These values do not, or weakly, correlate to the white blood cells obtained by the hematologic analyzer. The latter, under no circumstances, represent a reliable evidence of the concentration of CD34+ cells in CB.