Midpoint CD34 measurement as a predictor of PBPC product yield in pediatric patients undergoing high-dose chemotherapy.

High-dose chemo/radiotherapy of sensitive tumors requires PBPC rescue doses of > 3x10(6) CD34/kg (range: 3-20x10(6) CD34/kg). Because of the diversity of stem cell treatment protocols and clinical presentation of patients at the time of peripheral blood progenitor cell (PBPC) harvest, the use of the mid-point CD34 positive cell measurement was initiated to predict the final CD34-positive cell product yield/stem cell harvest. The measurement of CD34-positive cells at the mid-point of the initial setting of 5 total blood volumes (TBV) allows for the extension, shortening, or no change in the TBV processing to achieve a maximum goal of CD34-positive cells/kg body weight required for stem cell transplantation. The estimation of mid-point CD34-positive cells guided our center to extend 22 procedures, shorten 26 procedures, and leave 20 procedures unchanged. This investigation addresses three aspects of PBPC collection in pediatric patients: (1) the processing of large blood volumes (more than the defined 3 TBV and maximum up to 13 TBV in one session) to achieve good efficiency of the procedure; (2) the use of the mid-point CD34 measurement at 2.5 of 5 TBV initially set to predict the maximum goal of CD34 cells /kg needed on the same day of PBPC collection; and (3) PBPC collection in pediatric patients < 10 kg body weight (as low as 5.8 kg body weight).