Predictive value of the original content of CD34+ cells for enrichment of hematopoietic progenitor cells from bone marrow harvests by the apheresis procedure

We retrospectively investigated the feasibility of the apheresis procedure for red blood cell (RBC) reduction with a closed‐bag system. We also sought to determine the optimal processing volume for the maximal recovery of hematopoietic progenitor cells (HPC). Twelve bone marrow (BM) harvests were processed for major ABO‐incompatible allogeneic transplantation and one BM harvest was processed for autologous transplantation. The processing was performed through seven apheresis cycles with a two‐bag system using COBE Spectra Version 6.1. The mean recovery rates were compared in the products after four cycles and seven cycles of BM processing. Mean cell recovery rates were 79.2% (67.6–97.5%) and 87.3% (68.9–111.9%) for the mononuclear cells (MNC) and 84.5% (69.4–109.5%) and 92.0% (79.0–107.7%) for the CD34+ cells after four and seven cycles, respectively. A mean of 96.3% (93.0–98.1%) of the RBCs were finally removed. The yield of CD34+ cells after seven cycles of processing (median: 10.35 × 107 cells) was 7.9% greater than that after four cycles of processing (median: 9.65 × 107 cells), exhibiting a less‐than‐significant enhancement in yield. The CD34+ cell contents recovered in the concentrates up to four cycles (r = 0.989) and up to seven cycles (r = 0.993) were strongly correlated with the original content of the CD34+ cells. Engraftment was obtained in all patients except one patient infused with purified CD34+ cells. This latter result confirmed the hematopoietic potential of the cell populations recovered. Granulocyte recovery (defined as an absolute neutrophil cell count ≧ 500/μL for a period of three consecutive days) ranged from 8 to 25 days (median: 16 days) post‐transplantation. No hemolytic reaction was observed in any of the patients. Our results confirmed the efficacy of BM processing cycles with the COBE Spectra device. However, we could not conclude that the large‐volume apheresis for BM processing significantly enhanced the yields of HPC. The final recovery of CD34+ cells after processing could be predicted from the CD34+ cell content of the original collected marrow. J. Clin. Apheresis 2006. © 2006 Wiley‐Liss, Inc.