Correlations between hematopoietic progenitor cell counts as measured by Sysmex and CD34+ cell harvest yields following mobilization with different regimens.

PURPOSE

The Sysmex SE-9000 cell counter provides an estimate of immature cells referred to as hematopoietic progenitor cells (HPC). HPC counts should correlate with CD34+ counts in mobilized peripheral blood and apheresis to allow optimization of apheresis timing.

METHODS

We correlated the HPC counts as measured in the immature information channel with CD34+ cell levels as determined by FACS (HPCA-2 antibody, Becton Dickinson) from mobilized peripheral blood in 40 samples (27 patients and three healthy donors) and in aphereses ( n=113, 41 patients and 20 healthy donors).

RESULTS

In mobilized blood, HPC counts were correlated with CD34+ cells ( r=0.78, P<0.0001, n=40). The HPC counts were about 1.5-fold higher than CD34+ cell counts with a median (range) of 84 (1-747)/microl and 57 (1-370)/microl, respectively. In CD34+ selected cell preparations ( n=8), HPC counts were about fourfold lower than CD34+ cell counts with a median (range) of 179 (67-693)/microl and 760 (191-4309)/microl, respectively. In apheresis preparations, linear regression analyses were performed for the group of stem cell donors ( n=44), the group of lymphoma patients ( n=23), the multiple myeloma group ( n=21), and the group of solid tumors ( n=25). Interestingly, no correlation between HPC counts and CD34+ cell counts was found in the G-CSF-mobilized healthy donor group ( r=0.23, P=0.13). Pairing of HPC counts and CD34+ counts was effective in the group of patients receiving chemotherapy + G-CSF for stem cell mobilization: lymphoma group ( r=0.67, P=0.0005), multiple myeloma group ( r=0.56, P=0.008), and the group of solid tumors ( r=0.52, P=0.007).

CONCLUSIONS

Lymphoma and multiple myeloma patients who were moderately pretreated and mobilized with chemotherapy and G-CSF showed the best results in correlation analyses even at low HPC counts. Therefore, HPC measurement can be used for timing of apheresis in these patients.