Donor selection is one of the most difficult aspects of haploidentical stem cell transplantation (haplo-SCT) because many haploidentical donors are frequently available for a particular recipient. For a study, researchers conducted a prospective cohort study of 512 patients with hematological malignancies who had haplo-SCT to determine which donor variables were most important in favoring transplant outcomes in order to develop evidence-based guidance for donor selection in the setting of anti-thymocyte globulin-based haplo-SCT. 

Donor age was linked to worse overall survival (OS) [hazard ratio (HR) 1.08, P = 044]. Female donors to male receivers had a substantially higher non-relapse mortality (NRM; HR 2.05, P=006). Furthermore, increasing donor age was associated with an increased risk of Grades 3–4 acute graft-versus-host disease (aGVHD; HR 1.17, P = 005), and female donors to male recipients were associated with an increased risk of Grades 2–4 aGVHD (HR 1.50, P=002). In patients aged 35, sibling donors outperformed parental donors in terms of OS, disease-free survival, and NRM. In patients aged 35 years, however, sibling donors had greater NRM than offspring donors. 

When numerous haploidentical donors were available, a younger donor, generally a young sibling in younger receivers (aged 35) or a young child in older patients (aged 35), and avoiding female donors to male recipients, should be favored.