Systematic Scoping Review of Studies Reporting Unexpected Donor-Derived Abnormalities from Recipients of Allogeneic Hematopoietic Cell Transplantation: A Proposed Framework for Donor Disclosure.

Allogeneic hematopoietic cell transplantation (HCT) is used increasingly to treat blood and immune-based disorders. Post-transplantation testing of HCT recipients can lead to unexpected molecular, cytogenetic, and other information in donor-derived cells, raising questions regarding the potential impact on donor health. This study was conducted to identify the breadth of donor-derived abnormalities identified by testing HCT recipients and to determine the extent to which disclosure and donor follow-up are described. A systematic search and scoping review were conducted following PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) extension for scoping review guidelines in OVID MEDLINE and Embase (1947 to May 24, 2021). We identified 38 studies (63 donor-recipient pairs) addressing nonleukemic abnormalities to complement existing literature describing donor cell leukemia and donor-derived myelodysplasia. Donors were unrelated adults (n = 20), related family members (n = 28), cord blood donors (n = 6), or not reported (n = 9). Acquired cytogenetic, molecular, and morphologic abnormalities were reported. Donor origin was confirmed by cytogenetic analysis via karyotyping, fluorescence in situ hybridization, single tandem repeat PCR, and other techniques. A disease in donor-derived cells was described in 35 recipients (56.5%). Despite the relevance for testing and disclosure to donors, only 22 cases (32%) mentioned donor follow-up, and in 5 cases the donor developed a disease associated with the identified abnormality. Unrelated donor disclosure was mentioned in 3 of 26 cases (12%), with the findings reported back to the registry. Incidental abnormalities identified in transplanted donor cells may contribute to the post-transplantation risk of illness in the recipient and may be relevant to donor health. A framework for donor disclosure is proposed that incorporates consideration of analytic validity of the testing, potential significance of the finding, and the extent to which the abnormality is actionable. Adoption of effective processes to safeguard both donor and recipient health outcomes related to this issue is needed.