Impact of Hematopoietic Progenitor Cell Count as an Indicator for Optimal Timing of Peripheral Stem Cell Harvest in Clinical Practice

For optimizing CD34+ cell collection, appropriately timing peripheral blood stem cell harvest (PBSCH) initiation is crucial. Automatic cell analyzers with the immature myeloid information channel provide hematopoietic progenitor cell (HPC) count, a surrogate marker of CD34+ cells, which can be obtained within a few minutes without requiring monoclonal antibodies. The final decision on PBSCH initiation can be made using the HPC count obtained on the morning of the harvest day. Herein, we evaluated the impact of the HPC count as an indicator for the optimal timing of PBSCH in clinical practice over 9 years. One hundred and eighteen aphereses from 72 cases had a definite number of CD34+ cells/kg in the PBSC yield. A correlation was found between the HPC count in the PB and the CD34+ cell count (R = 0.563, p ＜ 0.001), whereas no correlation existed between the white blood cell and CD34+ cell counts (R = 0.0418, p = 0.65). We defined ＞ 2.0 × 106/kg of CD34+ cells in a single apheresis as good mobilization. Multivariate analysis demonstrated that an HPC count of ＞ 21/μL, myeloblast count of ＞ 12/μL, and age at PBSCH of ＜ 50 years were independently associated with good mobilization (p = 0.001, p ＜ 0.001, and p = 0.005, respectively). Our findings suggest that the HPC count is a good indicator for the optimal timing of PBSCH.