Q40: Chimerism Studies (Cord Blood Units and Non-Malignant Diseases)

*Chimerism Studies
This section relates to chimerism studies from allogeneic HCTs using cord blood units, or for allogeneic HCT recipients whose primary disease is non-malignant. If this was an autologous HCT, an allogeneic HCT using a bone marrow or PBSC product, and / or allogeneic HCT recipient whose primary disease for transplant was not a non-malignant disease, continue to the disease assessment section.

!Chimerism Studies
Chimerism study questions can only be completed on the Day 100, six-month, and one-year follow-up forms. These questions will be skipped for all subsequent reporting periods.

Chimerism studies are performed to determine the percent of blood or marrow cells post-transplant that are produced from donor hematopoietic stem cells and the percent that are produced from host (recipient) hematopoietic stem cells. Different types of blood cells and a variety of laboratory tests can be used to determine if a chimera (presence of both donor- and host-derived cells) exists. If cytogenetic testing was performed to look for disease markers, and the donor and recipient are different sexes, the test may also be used to determine if a chimera exists. If the donor and recipient are of the same sex, cytogenetic testing using the common staining technique, known as giemsa banding (G-banding), cannot be used to determine if there is a chimera. However, quinicrine banding (Q-banding) can be used to identify if the cells are of donor origin or not in a same-sex transplant, as this staining technique highlights inherited chromosome polymorphisms on certain human chromosomes including 3, 4, 13, 15, 21, 22, and Y. This is not a commonly used staining technique and is only helpful when the polymorphism is documented pre-HCT.

*Failed Chimerism Studies
If chimerism studies were attempted, but no evaluable results were obtained, report No, chimerism studies were not performed.

Question 40: Were chimerism studies performed?

Indicate whether chimerism studies were performed within the reporting period. If Yes, the Chimerism Essential Data (2451) Form will come due to report the chimerism study results.

Section Updates:

Question Number	Date of Change	Add/Remove/Modify	Description	Reasoning (If applicable)
Q40	1/23/2026	Modify	Updated Chimerism Studies blue info box: This section relates to chimerism studies from allogeneic HCTs using cord blood units, or for allogeneic HCT recipients whose primary disease is beta thalassemia or sickle cell disease only a non-malignant. If this was an autologous HCT, an allogeneic HCT using a bone marrow or PBSC product, and / or allogeneic HCT recipient whose primary disease for transplant was not beta thalassemia or sickle cell disease a non-malignant disease, continue to the disease assessment section.	Due to changes with the Oct 2025 quarterly release.

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