[Evaluation of routine blood cell counts in predicting the mobilization of CD34 positive cells]

The collection of peripheral blood stem cells (PBSC) is a crucial step for successful PBSC transplantation. Routine hematological parameters utilized for predicting the optimal timing of collection include white blood cell (WBC) counts, high fluorescence ratio (HFR) of reticulocytes, and platelet counts. We compared these parameters with the CD34-positive rates in the peripheral blood. In regimen with high-dose chemotherapy where the WBC count at nadir was lower than 1,000/microliter, we found that the maximum mobilization of PBSC was observed on the day when the WBC count reached 10,000/microliter. This coincidence was within about one day (mean 0.44, standard deviation 0.53). However, the reliability of the WBC count as a marker of PBSC mobilization varied among different harvest regimens. In the regimen with regular-dose chemotherapy where the WBC count at nadir was above 1,000/microliter, we could not find such a tight coincidence between the WBC count and PBSC mobilization. These results suggested that, in some situations, the measurement of the CD34-positive rate is mandatory for an efficient PBSC collection. We also found that the number of CD34-positive cells in the peripheral blood correlated (x) well to the amount of the CD34-positive cells actually harvested (y) (y = 0.524x + 0.249, r = 0.787). Thus, rapid fluorescence activated cell sorter (FACS) analysis of peripheral CD34-positive rates seemed to be extremely useful to predict the yield of PBSC collection.