Significance of peripheralCD_(34)~+ cell count on the harvest of mobilized peripheral hematopoietic stem cells

Abstract

：Objective Autologoushematopoietic stem cell transplantation (Auto-HSCT) has been widely used in hematologicalmalignancies.To mobilize and harvest sufficient number of peripheral CD_(34)~+ cells isone of key issues for auto-HSCT. Peripheral CD_(34)~+ cell numeration has been used as anindicator for apheresis while we mostly rely on the peripheral WBC or MNC count. In thisstudy, we try to evaluate the association of peripheral CD_(34)~+ count to the CD_(34)~+cells number in the apheresis product and to find out a potential threshold. Methods FromJan 2007 to Dec 2009, a total of 57 apherosis for auto-HSCT were analysed. All patientswere mobilized by cyclophophamide (CTX) plus G-CSF(5-10μg/kg) regimen. The apheresiswere performed with COBE SPECTRA VERSION 6 and CD_(34)~+ count of both peripheral andapheresis products were analysed by flow cytometry. Results The median number of MNC inapheresis products was 4.6(0.3-10.5)×10~8/kg with median CD_(34)~+ cells at2.4(0.16-34.9)×10~6/kg. The peripheral CD_(34)~+ count was the only parameter associatedwith the MNC and CD_(34)~+ cell numbers in the apheresis products while the WBC number wasirrelevant to the results of apheresis. Our data showed that when the peripheral CD_(34)~+count reach 15/μl, the efficacy of a single apheresis significantly improved with81 % and 60 % reached 1 and 2×10~6 CD_(34)~+ cells/kg respectively and the total numberof MNC and CD_(34)~+ cells were significantly superior to apheresis with peripheralCD_(34)~+ cells <15/μl, thus indicated that CD_(34)~+ ≥15 /μl canbe used as the threshold for apheresis. Furthermore, the ROC analysis demonstrated thatCD_(34)~+ cells ≥25(26.5-28.6) /μl is the best indicator levelfor a successful single apheresis. Conclusion Our study clearly showed that peripheralCD_(34)~+ cell count is a key indicator of apherosis. CD_(34)~+ cells at 15/μl can be used as the threshold tostart apheresis in the clinical setting. Key words: Peripheral blood stem cell transplantation; Antigens,CD_(34)~+; Apheresis