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

Abstract

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.

Patients and 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_s =0.846) overall and, in particular, under chemotherapy plus G-CSF (r_s =0.92) but correlated mildly under G-CSF monotherapy (r_s =0.655). AP-HPCs could not completely be dichotomized based on an AP-CD34⁺ threshold of 2×10⁶/kg for any stimulation procedure. In most cases with AP-HPCs >6×10⁶/kg, the AP-CD34⁺ count exceeded 2.0×10⁶/kg, but in 5.7% of these cases, the AP-CD34⁺ count was <2.0×10⁶/kg. A cut-off of AP-HPCs >4.843×10⁶/kg yielded a sensitivity of 71% and specificity of 96% for predicting AP-CD34⁺≥2×10⁶/kg.

Conclusion AP-HPCs can identify cases in which sufficient stem cells have been collected.