Novel and rapid enumeration method of peripheral blood stem cells using automated hematology analyzer

Introduction: The number of infused CD34⁺ cells is crucial to the success of peripheral blood stem cell transplantation (PBSCT). Here, we present, for the first time, a new method of enumerating hematopoietic progenitor cells (HPCs) for PBSCT. Method: This novel method is based on hemolysis and chemical staining, followed by flow cytometry-based optical detection, conducted using an automated hematology analyzer (XN series, Sysmex). CD34⁺ cells and HPCs were compared in 76 granulocyte colony-stimulating factor (G-CSF)-mobilized blood or apheresis samples taken from healthy donors (n = 18) or patients undergoing autologous PBSCT (n = 6). Results: There was a strong correlation between the numbers of HPCs and CD34⁺ cells (R² = 0.958). The expected total number of HPCs in the final products, which was estimated from HPCs in pre-apheresis PB or mid-apheresis products, also correlated well with the total number of CD34⁺ cells in the final products. The change in HPCs in PB closely resembled that of CD34⁺ cells during mobilization. Experiments using immunomagnetic beads suggested that the majority of CD34⁺ cells existed in HPCs, and vice versa. Conclusion: Hematopoietic progenitor cells may serve as surrogates for CD34⁺ cells in PBSCT. However, further investigations are required to verify this.