Use of total leukocyte and platelet counts to guide stem cell apheresis in healthy allogeneic donors treated with G-CSF

Healthy stem cell donors start leukapheresis 4 -5 days after starting G-CSF based on the peripheral blood CD34+ cell count (PBCD34). Data from 137 harvests (68 donors) were analyzed to determine correlation between pre-apheresis leukocytes (11.0-94.8 × 10⁹/l; median 38.8) and platelets (49-374 × 10⁹/l; median 180), and PBCD34 (3 -276/μl; median 40). PBCD34 correlated positively with leukocytes (r=0.48; P<0.0001) and platelets (r=0.40; P<0.0001). When pre-apheresis leukocytes were ≥25 and platelets were ≥100, PBCD34 and CD34+ collection were 5-276/μl (median 57) and 0.5-27.6 × 10⁶/kg (median 4.7), respectively; significantly higher than PBCD34 of 3-74/μl (median 17) and CD34+ collection of 0.2-8.9 × 10⁶/kg (median 2.2) when leukocytes were <25 and/or platelets were <100. With leukocytes ≥25 and platelets ≥100, PBCD34 was low (<20/μl) 8% of the time, compared to 57% of the time with leukocytes <25 and/or platelets <100 (P<0.0001). Our data suggest that it is not always necessary to measure PBCD34 to guide leukapheresis in healthy donors because pre-apheresis leukocytes and platelets ≥25 and ≥100, respectively, are associated with excellent mobilization. When blood counts do not meet these criteria, PBCD34 should be determined prior to initiation of apheresis.