Daily measurements of blood CD34+ cells after stem cell mobilization predict stem cell yield and posttransplant hematopoietic recovery.

The value of daily monitoring of the blood CD34+ cell concentration as a guide to the optimal timing of stem cell harvests was studied in 60 patients who underwent 66 stem cell mobilizations and 189 leukaphereses. There was a highly significant correlation between the blood CD34+ count and the CD34+ cell content in the apheresis product of the same day (r = 0.904, p < 0.01). Thus, the target yield of 4 x 10(6) CD34+ cells/kg can be harvested in one or two leukaphereses when the blood CD34+ cell count exceeds 50 x 10(6)/L. However, an insufficient harvest is to be expected when the blood CD34+ cell count is below 20 x 10(6)/L. The data from 35 autologous blood cell transplantations with a minimum CD34+ cell yield of 1.5 x 10(6)/kg showed that the recovery of blood neutrophil counts to 1.0 x 10(9)/L occurred in all patients within 9-14 days, but the time to recovery of the platelet counts to 20 x 10(9)/L may exceed 14 days, especially if the CD34+ cell content is below 4 x 10(6)/kg. Daily monitoring of blood CD34+ cell counts is a rapid and reliable means to guide the timing of stem cell collections. The count predicts well the CD34+ cell content of the harvests, the number of leukaphereses needed, and the speed of hematopoietic recovery.