Background: Cord blood (CB) represents an alternate source of stem cells in transplantation. Nucleated red blood cells (NRBCs) are a physiological subset of CB population. Although it is important to have an accurate estimate of CD34(+) cell number, NRBCs could compromise white blood cell count and interfere with CD34(+) cell quantification.
Study design and methods: A total of 826 CB units were analyzed for total nucleated cells (TNCs), NRBCs, and CD34(+) cells by flow cytometry. NRBCs were also counted conventionally by manual microscopy. Percentages of CD34(+) cells corrected by NRBC count (CD34+c) were determined as follows: %CD34+c = CD34(+)/CD45(+) (x10(6))/(TNCs (x10(8)) - NRBCs (x10(8))).
Results: The mean percentages of CD34+ cells and NRBCs were 0.27 percent (range, 0.01%-1.25%) and 7.64 percent (range, 0.13%-84%), respectively. Comparison between flow cytometric and microscopic NRBC count showed a regression of y = 0.685 + 0.719x and a coefficient of determination of r(2) = 0.721. When corrected with NRBC count, the mean percentage of CD34(+) c cells was 0.295 percent (p = 0.0008 compared with CD34(+)%) and mean TNCc count was 14.8 x 10(8) (p < 10(-4) compared to TNC count).
Conclusion: The determination of NRBCs with a flow cytometric method might represent a new strategy for providing satisfactory quality assurance controls of CB products.