Direct volumetric flow cytometric quantitation of CD34+ stem and progenitor cells.

Objectives: In this study, we compared a classic single-platform (SP) method applying beads for enumeration of CD45+ or CD34+ cells with a new device allowing direct volumetric measurements of stem and progenitor cells. Background: Following apheresis and cyropreservation, the precise enumeration of CD34+ cells as key parameter of graft quality is mandatory for the clinical course after transplantation. Currently, flow cytometry with SP technique represents the gold standard for such determinations. Methods/Materials: Fresh samples, 14 from mobilised peripheral blood (PB), 9 from apheresis products (AP) and 13 samples from frozen-thawed (FT) haematopoietic progenitor cell grafts, were analysed for CD34+ cells, CD45+ cells, and in frozen-thawed samples for viability by a bead-based flow cytometric method and in parallel by a direct, volumetric flow cytometric method. Results: Comparison of CD34+ analyses revealed a significant correlation (P < 0.01) for each material between both techniques with r = 0.95 (PB), r = 0.933 (AP) and r = 0.929 (FT). Also, for analysis of CD45+ cells mu L-1, the measured numbers evaluated with the different techniques did not significantly differ for all three materials analysed. In frozen-thawed samples, the analysis of viability was comparable for both techniques. Conclusions: The results of this study demonstrate that a direct volumetric analysis of CD34+ cells mu L-1 or CD45+ cells mu L-1 is feasible. This technique represents a simple and economical approach for standardisation of progenitor and stem cell analyses.