The number of infused CD34+ cells is crucial to the success of peripheral blood stem cell transplantation (PBSCT). Although counting CD34+ cells currently depends solely on flow cytometry technology, the complexity of the procedure and the high cost of reagents (including monoclonal antibodies) are the main disadvantages. The SYSMEX SE-9000 (SE) and XE-2100 (XE) automated hematology analyzers quickly estimate the number of immature cells, referred to as hematopoietic progenitor cells (HPCs), at very low cost. The number of peripheral blood SE/XE-determined HPC (SE/XE-HPC) is used to determine the optimal timing of peripheral blood stem cell (PBSC) collection. However, SE/XE-HPCs are limited as a substitute for CD34+ cells because they are likely to be affected by co-existing immature cells (e.g. immature granulocytes), resulting in overestimation of the HPC count. Therefore, we developed a new technology for counting HPCs. The assay's mechanism is based on finely-tuned hemolysis reactions and chemical staining with a specific dye, and does not require monoclonal antibodies. The assay is followed by a flow cytometry-based optical detection technique that differs from the SE or XE former types, which use the electrical radiofrequency/direct currency impedance detection method. This modified program has been installed into an revised model of an automated hematology analyzer, the XN Prototype (SYSMEX corporation, Kobe, Japan), which enables us to cost-effectively obtain the number of new, marked HPCs, designated as 'XN-determined HPC (XN-HPC)', within 4 minutes using small (200 μL) samples. The purpose of this study is to evaluate the XN-HPC in comparison with CD34+ cells, and this is the first report of the results.
Between 2008 and 2011, a total of 87 blood or G-CSF-mobilized apheresis samples were taken from healthy donors (n=20) or patients undergoing autologous PBSCT (n=5) at the National Cancer Center Hospital, Japan. Next, CD34+ cells and XN-HPCs were analyzed in the same samples. XN-HPCs were counted using the XN Prototype, and CD34+ cells were quantified using a flow cytometer (FACSCalibur, BD, New Jersey, USA) using the dual platform method according to the International Society of Hematology and Graft Engineering protocol. This study was approved by Institutional Review Board, and informed consent was obtained from all patients.
Tanosaki:Sysmex Corporation: They provided hematology analyzers, a flow cytometer and reagents.
Asterisk with author names denotes non-ASH members.