ESTIMATION OF THE PROGENITOR-CELL YIELD IN A LEUKAPHERESIS PRODUCT BYPREVIOUS MEASUREMENT OF CD34-BLOOD( CELLS IN THE PERIPHERAL)

To assess whether measurement of CD34+ cells in the peripheral blood a llows one to estimate the progenitor cell yields of subsequent leukaph eresis procedures, 733 corresponding blood and leukapheresis samples w ere analyzed. Peripheral blood progenitor cells of cancer patients wer e mobilized with hematopoietic growth factors alone or postchemotherap y, and harvested processing 10 liters of blood for each leukapheresis product. The CD34+ cell count (CD34+ cells/mu l blood) correlated most closely with the progenitor cell yield in the corresponding leukapher esis product (CD34+ cells/kg bodyweight, r = 0.80), while the proporti on of circulating CD34+ cells to the white blood and mononuclear cells predicted the yield less reliably (r = 0.74 and r = 0.60). The CD34cell yield was independent of the white blood count (r = 0.04), wherea s a weak correlation was found between the mononuclear cell count and the number of CD34+ cells/kg collected (r = 0.42). It was unlikely to obtain the threshold quantity of 2.5 x 10(6) CD34+ cells/kg required f or rapid engraftment when counts below 10 CD34+ cells/mu l blood were detected. At levels between 10 and 30 CD34+ cells/mu l sufficient auto grafts could be harvested, whereas 30-100 CD34+ cells/mu l were requir ed to achieve this by a single leukapheresis. A surplus of CD34+ cells was likely above 100 CD34+ cells/mu l which could be useful for proge nitor cell enrichment techniques, The correlation between the CD34+ ce ll count and progenitor cell yield was independent of the mobilizing r egimen and whether leukaphereses had been performed previously. In con clusion, the number of CD34+ cells/mu l blood allows a reliable predic tion of the CD34+ progenitor cell yield in subsequent leukapheresis pr ocedures. However, rare cases of unexpectedly sufficient progenitor ce ll yields may be observed even at CD34+ cell levels below detection li mit.