Hematopoietic Progenitor Cell Counts of the Leukapheresis Product Determined Using Sysmex XN Analyzers Predict a Sufficient Number of CD34 Stem Cells in a Peripheral Blood Stem Cell Harvest for Autologous Transplantation.

Objective Several institutions outsource CD34 cell counting of leukapheresis products, limiting rapid measurements, as results are obtained the next day. This problem is compounded with plerixafor use, a stem cell-mobilizing drug that increases leukapheresis efficiency but requires administration the day before leukapheresis. Use of this drug for a second leukapheresis procedure before the first-day leukapheresis CD34 count results are confirmed causes unnecessary leukapheresis and expensive plerixafor administration. We investigated whether or not measuring hematopoietic progenitor cells in leukapheresis products (AP-HPCs) using a Sysmex XN-series analyzer could resolve this problem. Methods We retrospectively compared the absolute AP-HPC value per body weight with the CD34 (AP-CD34) count in 96 first-day leukapheresis product samples obtained between September 2013 and January 2021. Comparisons were also conducted according to regimen: granulocyte colony-stimulating factor (G-CSF) monotherapy, chemotherapy plus G-CSF, or plerixafor mobilization. Results AP-CD34 and AP-HPC counts correlated strongly (r=0.846) overall and, in particular, under chemotherapy plus G-CSF (r=0.92) but correlated mildly under G-CSF monotherapy (r=0.655). AP-HPCs could not completely be dichotomized based on an AP-CD34 threshold of 2×10/kg for any stimulation procedure. In most cases with AP-HPCs >6×10/kg, the AP-CD34 count exceeded 2.0×10/kg, but in 5.7% of these cases, the AP-CD34 count was <2.0×10/kg. A cut-off of AP-HPCs >4.843×10/kg yielded a sensitivity of 71% and specificity of 96% for predicting AP-CD34≥2×10/kg. Conclusion AP-HPCs can identify cases in which sufficient stem cells have been collected.