[Effect of processed blood volume, leukocyte count and concentration of CD34-positive cells in peripheral blood on efficiency of stem cell apheresis].

Despite many published studies no parameter could be identified yet to acceptably and individually predict collection results in stem cell apheresis. We analyzed leukocyte counts and processed blood volume, absolute and relative CD34+ cell counts, and overall collection efficiency in 120 patients with hematological and solid malignancies (354 leukaphereses using the Cobe Spectra cell separator, a median of 3 per patient, span 1-9). Stem cells were mobilized into peripheral blood by conventional chemotherapy followed by daily doses of G-CSF. CD34+ progenitor cell counts were monitored through multiparametric flow cytometry. Blood and collection flows varied in the range of 45-90 ml/min and 0.7-1.5 ml/min, respectively. CD34+ progenitor cells were enriched 38-fold in the apheresis product as compared to peripheral blood at a processed blood volume lower than one total blood volume. Efficiency continuously declined, on to a 25-fold concentration at a processed blood volume above the 3-fold total blood volume. Total collection efficiency, calculated from the absolute content of CD34+ progenitor cells in peripheral blood and apheresis concentrate (a parameter for progenitor cell mobilization during the apheresis), reached a plateau at a processed blood volume above the 3-fold total blood volume. However, variation among individual patients was high. The concentration rate of CD34+ cells at a leukocyte count below 5,000/microliter averaged 50 and declined continuously to 8 at leukocyte counts between 45,000 and 50,000/microliter. To summarize, in 70% of patients with leukocyte counts below 5,000/microliter and CD34+ progenitor cell counts above 10,000/ml, more than 1.5 x 10(6) progenitors per kg body weight could be collected in a single leukapheresis. According to the presented data, the variation in overall collection efficiency is mainly due to: 1) varying mobilization of progenitors during the apheresis procedures itself and 2) dependence on peripheral leukocyte counts.