Background: There is a large inter-individual variation in CD34+ cell yield after G-CSF mobilisation and collection from peripheral blood in healthy allogenic haematopoietic stem cell donors. Donor characteristics including gender and age, baseline and precollection blood results, mobilisation factors and collection factors have been associated with CD34+ cell concentration in the blood after G-CSF mobilisation and/or CD34+ cell yield after collection. Since the literature reporting these associations is heterogeneous, we here clarify the determinants of CD34+ cell concentration and yield through a scoping literature review. Materials and Methods: MEDLINE, Embase, PubMed and Stem Cell Evidence were searched for studies published between 2000 and 2023. The inclusion criteria were studies of allogeneic donors undergoing G-CSF mobilisation and peripheral blood stem cell collection (PBSC). Eligible studies assessed an outcome of mobilisation or collection efficacy, indicated by the blood CD34+ cell concentration after 4 or 5 days of G-CSF treatment and/or CD34+ cell yield in the first PBSC collection after mobilisation. Included studies assessed associations between these outcomes and donor factors(such as age, gender, weight, ethnicity), mobilisation factors (G-CSF scheduling or dose), collection factors (venous access, processed blood volume) and laboratory factors (such as blood cell counts at baseline and after mobilisation). Results: The 51 eligible studies evaluated between 23 and 20,884 donors. 43 studies were retrospective, 32 assessed blood CD34+ cell concentration after mobilisation and 37 assessed CD34+ cell yield. In studies that recorded both outcomes, blood CD34+ cell concentration always predicted CD34+ cell yield. The most frequently assessed factor was donor age for which most studies reported that younger donors had a higher blood CD34+ cell concentration and CD34+ cell yield. Non-European ancestry was associated with both higher blood CD34+ cell concentration and yield although this finding was inconsistent. Conclusions: There remains poor consensus about the best predictors of blood CD34+ cell concentration and yield that requires further prospective study, particularly of the role of donor ancestry. The current focus on donor gender as a major predictor may require re-evaluation

The authors have declared no competing interest.

This study did not receive any funding

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