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.

Question 89-90: Were chimerism studies performed post-HCT? (Allogeneic HCTs only)

Indicate whether chimerism studies were performed within the reporting period. If “yes,” continue with question 90 and indicate whether documentation was submitted to CIBMTR (e.g., chimerism laboratory reports).

If chimerism studies were not performed within the reporting period, select “no,” and continue with question 108.

Question 91: Were chimerism studies assessed for more than one donor / multiple donors?

Indicate whether this HCT included product(s) from multiple donors. When a multi-donor chimerism exists and includes a donor or donors from a previous HCT, report as a multi-donor chimerism even though there may only be one donor for the current transplant.

Questions 92-107: Provide date(s), method(s) and other information for all chimerism studies performed prior to the date of contact (question 1)

Transplant centers may perform frequent chimerism studies. If there is a need to reduce the number of chimerism study results reported due to volume, ensure that the following are reported at a minimum:

  • Studies performed on or at approximately Day+28
  • Most recent studies performed prior to the date of contact, particularly for Day+100
  • Most recent studies performed prior to and after an intervention (such as a donor cellular infusion)
  • The first result to show complete / 100% donor chimerism

Chimerism – Single Donor

Data Field Description
92. NMDP donor ID If the donor or one of the donors was an NMDP PBSC or marrow donor, enter the 9 digit NMDP donor ID.
93. NMDP cord blood unit ID If the donor or one of the donors was an NMDP cord blood unit, enter the 9 digit NMDP cord blood unit ID.
94. Non-NMDP unrelated donor ID If the donor or one of the donors was a non-NMDP unrelated PBSC or marrow donor, enter the non-NMDP registry donor ID.
95. Non-NMDP cord blood unit ID If the donor or one of the donors was a non-NMDP cord blood unit, enter the non-NMDP registry donor ID.
96. Date of birth or age If the donor was related or the cord blood unit was related or supplied by a non-NMDP registry, provide the date of birth, if known; if date of birth is not known, provide the donor’s age at donation.
97. Sex If the donor was related or the cord blood unit was related or supplied by a non-NMDP registry, provide the biological sex.
98. Date sample collected Enter the date the sample was collected for the chimerism test.
99-100. Method Report the test method used for the reported chimerism study. Cytogenetic testing methods include karyotyping and fluorescent in situ hybridization (FISH). Cytogenetic methods are only valid for sex mismatched transplants with the exception of quinicrine banding. VNTR / STR is one of the most common molecular methods for assessing chimerism. See the Chimerism Methods table below for additional details on chimerism testing methods.
101. Cell source Report whether the specimen taken for chimerism testing was from a marrow or peripheral blood source.
102-103. Cell type Indicate the cell type tested. If the specimen was not sorted for a specific cell line, indicate “unsorted / whole.” See the Chimerism Cell Types table below for additional details on cell markers unique to certain cell lines.
104. Total cells examined Cytogenetic testing methods include karyotyping and fluorescent in situ hybridization (FISH), each of which examines a specific and relatively low number of cells – generally 15 to 200, depending on specimen and test method. If a cytogenetic method was used, enter the total number of cells that were examined. If a non-cytogenetic test was used, leave these boxes blank.
105. Number of donor cells Cytogenetic methods, karyotyping and FISH, examine a specific and relatively low number of cells – generally 15 to 200, depending on specimen and test method. If a cytogenetic method was used, enter the total number of cells that were examined and found to be of donor origin. If a non-cytogenetic test was used, leave these boxes blank.
106. Were donor cells detected? Molecular testing methods include RFLP and VNTR / STR. If a molecular method was used, indicate whether donor cells were detected. Report “yes,” if the testing identified any percentage of cells as being of donor origin.
107. Percent donor cells Molecular testing methods include VNTR / STR, RFLP, and AFLP. Report the percentage of donor cells identified by molecular testing. If the test result did not detect any recipient cell population within the sensitivity of the assay, report 100% donor cells. If the test detected recipient cells, but indicated donor cells “> n%,” report “n + 1” percent donor cells. If the test detected donor cells but indicated donor cells “< n%,” report “n – 1” percent donor cells.

Chimerism Methods

Method Description
Karyotyping for XX / XY Cells are grown in culture, stained, and examined under a microscope to identify the number of cells matching the sex of the donor. This method is only valid when donor and recipient are sex mismatched.
Fluorescent in situ hybridization (FISH) for XX / XY Cells are exposed to fluorescent DNA probes which attach to X and Y chromosomes. A microscope is used to identify the *number *of cells matching the sex of the donor. This method is only valid when donor and recipient are sex mismatched. Do not report FISH testing for disease-specific abnormalities in the chimerism section of the Post-TED.
Restricted fragment length polymorphisms (RFLP) A restriction fragment is a portion of DNA which has been cut out by an enzyme. RFLP testing begins by isolating DNA from the sample. Enzymes are used to cut the DNA at specific loci resulting in many unique restriction fragments. The fragments are separated according to size by electrophoresis. The unique pattern of separation is used to identify the percent donor DNA present in the sample.
Variable number tandem repeat (VNTR), micro- or minisatellite VNTR refers to a portion of DNA containing a repeating sequence of base pairs (micro- or minisatellite). The number of times a micro- or minisatellite repeats within specific loci can differ between individuals. These differences are used to distinguish donor DNA from recipient DNA. VNTR testing involves obtaining samples from the recipient and donor prior to transplant. Specific loci are compared to determine which loci contain VNTRs unique to the donor. After transplant, DNA is isolated from recipient samples. Donor-specific VNTRs are amplified by PCR techniques. The sample is then analyzed to determine the percent donor DNA present.
Small tandem repeat (STR), micro- or minisatellite STR also refers to a portion of DNA containing a repeating sequence of base pairs (micro- or minisatellite). The number of times a micro- or minisatellite repeats within specific loci can differ between individuals. These differences are used to distinguish donor DNA from recipient DNA. STR testing involves obtaining samples from the recipient and donor prior to transplant. Specific loci are compared to determine which loci contain STRs unique to the donor. After transplant, DNA is isolated from recipient samples. Donor-specific STRs are amplified by PCR techniques. The sample is then analyzed to determine the percent donor DNA present.
Amplified fragment length polymorphisms (AFLP) A restriction fragment is a portion of DNA which has been cut out by an enzyme. AFLP testing begins by isolating DNA from the sample. Enzymes are used to cut the DNA at specific loci resulting in many unique restriction fragments. Many restrictions fragments are amplified using PCR techniques. The fragments are separated according to size by electrophoresis. The unique pattern of separation is used to identify the percent donor DNA present in the sample. Report AFLP testing using the VNTR/STR method option on the 2450 form.

Chimerism Cell Types

Cell Type Description
Unsorted / whole The peripheral blood or bone marrow sample has not been sorted or selected for a certain cell line.
Red blood cells Also known as RBCs or erythrocytes; carry the CD235a cell marker
Hematopoietic progenitor cells Includes CD34+ cells
Total mononuclear cells Total mononuclear cells would be a specimen containing only and both lymphocytes and monocytes
T cells Includes CD3+, CD4+, and / or CD8+ cells
B cells Includes CD19+ or CD20+ cells
Granulocytes Also known as polymorphonuclear leukocytes (PMNs, PMLs) and includes neutrophils, eosinophils, and basophils. Includes CD33+ cells
NK cells Includes CD56+ cells
Other, specify Use this option to report cell types that do not fit in a category above.
Last modified: Jul 07, 2020

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