Meredith G. Parsons

Purpose A critical component of optimizing peripheral blood (PB) hematopoietic stem cell (HSC) collections is accurately determining the processed blood volume required to collect the targeted number of HSCs. Fundamental to most truncation equations employed to determine this volume is the procedure's estimated collection efficiency (CE), which is typically applied uniformly across all HSC collections. Few studies have explored the utility of using different CEs in subpopulations of donors that have substantially different CEs than the institutional average. Methods Initial procedures from 343 autologous and 179 allogeneic HSC collections performed from 2018 to 2021 were retrospectively analyzed. Predictive equations were developed to determine theoretical truncation rates in various donor subgroups. Results Quantitative variables (pre‐procedure cell counts) and qualitative variables (relatedness to recipient, gender, method of venous access, and mobilization strategy) were found to significantly impact CE. However, much of the variability in CE between donors could not be explained by the variables assessed. Analyses of procedures with high pre‐collection PB cell counts identified lower CE values for these donors' truncation equations which still allow truncation but minimize risk of collecting less CD34+ cells than requested. Conclusions Individualized CE does not substantially improve truncation volume calculations over use of a fixed CE and adds complexity to these calculations. The optimal fixed CE varies between autologous and allogeneic donors, and donors with high pre‐collection PB cell counts in either of these groups. This model will be clinically validated and continuously refined through analysis of future HSC collections.