Efficiency of day 4 compared to day 6 stem cell mobilization in allogeneic stem cell donors

Background: Granulocyte colony stimulating factor (G-CSF) given for 4-6 days is commonly used for mobilization of allogeneic stem cell donors. The primary objective of this study is to compare the yield of stem cell mobilization, assessed using a surrogate endpoint of CD34+ cell count, between Day 4 and Day 6. Study design and Methods: In this retrospective study we included all allogeneic stem cell donors mobilized with G-CSF for 6 days from January 2003 until October 2015 in the bone marrow transplantation unit at a tertiary academic center. Of 106 donor records reviewed, 84 were with available data and selected for the study. Results: We included 84 donors with median age and weight of 19 years and 60 kg respectively. The median Day 4 WBC and CD34(+) cell count were 37.4 x 10(9)/L and 54 x 10(6)/L respectively; while the median Day 6 WBC and CD34(+) cell count were 44.4 x 10(9)/L and 86 x 10(6)/L respectively with a statistically significant difference from Day 4 (P < 0.001). In the multivariable model, there were no significant impact of donor's age (P = 0.215), weight (P = 0.108), height (P = 0.428) and mean corpuscular volume (P = 0.263) on the difference in CD34(+) cell yield. However, the donor's blood group AB predicated a significantly higher difference (P = 0.036). Conclusion: Six days of G-CSF mobilization achieves higher CD34(+) cell count than 4 days in allogeneic stem cell donors especially in donors with blood group AB, albeit both approaches give count higher than the successful collection threshold.