Donor characteristics and intraoperative total nucleated cell count influence hematopoietic progenitor cell yield of healthy donor bone marrow grafts.

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Bone marrow graft cell content impacts engraftment potential after allogeneic hematopoietic cell transplantation (alloHCT). Surrogates, such as intraoperative total nucleated cell count (ioTNC), are of unclear utility in predicting final graft characteristics. In addition, demographic and clinical factors may influence graft cellular profile and recipient engraftment. We retrospectively reviewed marrow harvests at our institution performed between 2009 and 2019. During this time, an ioTNC was measured after 50% of the projected final graft volume was collected. Regression models were used to assess associations between ioTNC (cells/µL) and final graft CD34+ (cells/mL), and between graft and donor characteristics and final graft CD34+ (cells/mL). Fifty-three marrow harvests and donor-recipient pairs were analyzed. Median (range) donor and recipient ages were 13 (0.7-28) years and 9 (0.2-21) years, respectively. The median ratio of donor/recipient weight was 1.225kg (range 0.31-7.13). Median total volume of harvested marrow was 15.3mL/kg (range 4.3-20.4) of donor weight and 19.4mL/kg (range 4.7-87.4) of recipient weight. Median ioTNC was 20930/µL (range 6600-44310) or 2.1×109 /mL, corresponding to median predicted final graft TNC of 3.59×108 /kg recipient weight (range 1.28-19.42×108 ). Simple linear regression between ioTNC and CD34+ cells/mL resulted in an R2 of 0.42. Least absolute shrinkage and selection operator (LASSO) regression produced a moderately predictive model consisting of ioTNC, donor age, and donor weight (adjusted R2 =0.7) of final graft CD34+ cells/mL. ioTNC and certain donor characteristics correlate moderately well with marrow product CD34+ cells/mL, potentially informing donor selection and marrow procurement strategies.