Collection of peripheral blood progenitor cells (PBPC) based on a rising WBC and platelet count significantly increases the number of CD34+ cells.

The kinetics of mobilization and optimal timing of peripheral blood progenitor cell (PBPC) collection were evaluated in 190 patients with multiple myeloma undergoing stem cell harvest after mobilization with cyclophosphamide, prednisone and G-CSF. There was a strong correlation between the WBC count and the number of CD34+ cells circulating in peripheral blood (r = 0.875). Initiating leukapheresis based on rising WBC and platelet counts rather than on a fixed day increased the mean number of CD34+ cells 115% (9.7 to 20.9 x 10(6) CD34+ cells/kg; P = 0.010) for the total of all leukaphereses and 59% for the total of all CD34-selected products (5.1 to 8.1 x 10(6) CD34+ cells/kg; P = 0.011). Although the yield and purity of the CD34-selected product were not significantly affected (P > or = 0.071), the percentage of patients with concentrations of CD34+ cells in the initial leukapheresis of > 1% increased from 47% to 70% (P = 0.004). The mean purity of the selected product was related to the starting percentage: 48.9% if < 1% and 81.5% if > or = 1% (P < 0.001). Collection of stem cells based on rising WBC and platelet counts significantly increased the number of CD34+ cells in leukaphereses and CD34-selected products in comparison with collection on a fixed day.