Correlation of hematopoietic progenitor cell count determined by the SE-9000TM automated hematology analyzer with CD34+ cell count by flow cytometry in leukapheresis products

The yield of stem cell collection after mobilization is crucial for autologous peripheral blood stem cell (PBSC) transplantation. Quantitative determinations of CD34+ cells using flow cytometry or stem cell culture have been used, but these methods require much time, technical experience, and expensive reagents. The automated hematology analyzer (Sysmex SE-9000TM, TOA, Japan) equipped with the Immature Information (IMI) channel for immature myeloid cells can detect IMI+ cells within 90 sec. Detection is made possible by the combination of a special reagent system and direct current/radiofrequency biosensors. We studied the relation of IMI+ cells and variable cell counts with CD34+ cell yield in autologous stem cell harvest. In a series of 32 patients (median age, 44 years; M:F = 11:21), 184 leukaphereses were performed after mobilization regimens with chemotherapy and G-CSF or G-CSF alone. Full blood cell counts were enumerated on peripheral blood (PB) samples taken prior to each leukapheresis. Mononuclear cell (MNC) and IMI+ cell counts by automated hematology analyzer and flow cytometry based CD34+ cell yield were measured on the harvested product. The relationship among PB white blood cells (WBC), PB monocytes, IMI+ cells, MNC, and CD34+ cell yield in a single leukapheresis was estimated by Pearson correlation analysis. PB WBC count showed no correlation with CD34+ cell yield in a single leukapheresis (r = 0.02, P = 0.81). PB monocyte count showed a weak correlation (r = 0.21, P = 0.01) and MNC in harvest also showed a weak correlation (r = 0.36, P = 0.0001) with CD34+ cell yield. In contrast, CD34+ cell yield correlated well with IMI+ cell count (r = 0.68, P = 0.0001), and data could be fitted by a linear regression equation, y = 0.330 + 0.974x. IMI+ cell assay by the automated hematology analyzer correlated well with the CD34+ cell yield in a mobilized autologous stem cell harvest. The IMI+ cell count might be used as a simple and efficient indicator of blood stem cell mobilization and collection.