JOURNAL OF HEMATOTHERAPY & STEM CELL RESEARCH 10:17–18 (2001) Mary Ann Liebert, Inc. Correspondence Correlation Coefficients Between Several Parameters and CD34 1 Cell Yield in Peripheral Blood Stem Cell Harvesting by Apheresis JOSÉ R. BORBOLLA, 1 ALEJANDRO NÁJERA, 2 MANUEL A. LÓPEZ-HERNÁNDEZ, 2 MAURICIO GONZÁLEZ, 2 ALBERTO SILLER, 1 BENJAMÍN RUBIO, 3 OSCAR GARCÉS, 3 JOSÉ LUIS DELGADO, 3 and MARIA T. COLLADOS 4 17 To the editor: One major practical issue to consider in the process of peripheral blood stem cell (PBSC) har- vesting is when to start, and a reasonable answer is: “When the conditions are optimal for obtaining enough PBSCs with as few apheresis procedures as possible”. Both preharvest white blood cell (WBC) and mononu- clear cell counts (MNC) hold a poor correlation to the CD34 1 yield of the apheresis procedures (1–3). Yu et al. (1) found correlation coefficients of harvested CD34 1 cells to that of WBC and MNC, r 5 0.12 and r 5 0.35, respectively. Schwella et al. (2) reported coefficients of r 5 0.35 and r 5 0.49, and Perez-Simon et al. (3) of r 5 0.18 and r 5 0.25 for the same parameters. In contrast, correlations between preharvest CD34 1 cell counts and the number of harvested CD34 1 cells are usually very high, for example, r 5 0.87, (1) 0.92, (2) and 0.9 (3). Our group is currently studying the correlation coefficients between several parameters to identify the best indicator to start the apheresis collection of PBSC for transplant. Until now, we have studied 44 apheresis procedures in 23 patients undergoing PBSC harvesting for transplanta- tion, including 8 males and 15 females. The mean age was 33.3 years (median 35, range 4–50). Diagnoses included 4 patients with CML, 7 with breast cancer, 4 with acute nonlymphoblastic leukemia, 3 with multiple myeloma, 3 with acute lymphoblastic leukemia, and 2 with non- Hodgkin’s lymphoma. Mobilization was done using a sin- gle dose of cyclophosphamide (4 g/m 2 ) followed by gran- ulocyte colony-stimulating factor (G-CSF) (10 mg/kg daily) until the last procedure was done. The mean num- ber of apheresis procedures was 1.9 (range 1–4). As found by other groups, the variable that correlated best for har- vested CD34 1 cells was the number of CD34 1 cells found in the circulation prior to apheresis (r 5 0.74). Other vari- ables showed very little correlation. (Table 1). Thus, it is clear that, to obtain the highest yield of PBSC, it is better to start harvesting when the number of CD34 1 cells in peripheral blood is high. Different au- thors recommend different minimal CD34 1 blood counts to start harvesting ranging from 5–50/ ml (1–5). Although it would seem reasonable to wait until a large number of these cells are found in the peripheral blood, there are economical concerns associated with delay. The ideal number of CD34 1 cells per microliter to start har- vesting is both a matter of discussion and a matter of lo- cal conditions; that is, what is more expensive in a given location, the additional cost of hospital stay and G-CSF, or performing three or more, instead of one or two aphere- sis procedures? REFERENCES 1. Yu J, W Leisenring, WI Bensinger, LA Holmberg and SD Rowley. (1999). The predictive value of CD34 1 cell count in the peripheral blood for timing apheresis and maximizing yield. Transfusion 39:442–450. 2. Schwella N, J Beyer, I Schwaner, HG Heuft, O Rick, D Huhn, S Serke and W Siegert. (1996). Impact of preleuka- pheresis cell counts on collection results and correlation of progenitor cell-dose with engraftment after high-dose chemotherapy in patients with germ cell cancer. J Clin On- col 14:1114–1121. 1 Stem Cell Transplant Program, Hospital San José-Tec de Monterrey, Monterrey, Nuevo León, México. 2 Hematology Department, Centro Médico Nacional “20 de Noviembre,” I.S.S.S.T.E. México City, México. 3 Hematology Department, Centro Médico de Occidente, IMSS, Guadalajara, Jalisco, México. 4 Centro de Investigación y Extensión de Ciencias de la Salud, División de Ciencias de la Salud, Instituto Tecnológico y de Estudios Superiores de Monterrey, Monterrey, Nuevo León, México.