Chimerism by STR (Postransplant) Patients receiving hematopoietic cell infusions for engraftment, such as bone marrow transplant patients, should have the percentage of donor and recipient cells in their blood or bone marrow monitored. The presence of both cell types (Chimerism) or only donor cells is a sign that the transplant was successful.

Why is this test recommended?

• After a hematopoietic stem cell transplant, patients undergo chimerism testing (engraftment analysis).
• The test entails determining the genetic profiles of the donor and recipient and determining the degree of genetic mixing in the recipient's blood or bone marrow.
• Before the transplant, the recipient's and potential donors' DNA is separated, and analysis is done to see if the genetic markers specific to the donor and recipient can tell the donor from the recipient
• . The performance of the transplant engraftment is then evaluated following the transplant by comparing the contribution of donor vs recipient white blood cells in post-transplant blood or bone marrow specimens collected from the recipient.

Procedure:

• The patient, donor, and post-transplant samples isolate the DNA.
• The Promega GenePrint24 System uses a method commonly used in human identity testing to amplify DNA.
• This is done by analysing genomic polymorphisms known as short tandem repeat (STR) loci.
• For each subsequent post-transplant specimen, a longitudinal plot of historical data is created along with the calculation and reporting of the donor chimerism percentage.
• The analysis of genomic polymorphisms known as short tandem repeat (STR) loci is how chimerism testing (also known as engraftment analysis) by DNA is carried out.
• This technique is frequently used in human identity testing. These loci are made up of a core DNA sequence that is repeated inside a particular genetic locus several times.
• The length of a tandemly repeated core DNA sequence, which varies in size from 2 to 8 base pairs, is called a microsatellite.

These loci display codominant Mendelian features that can have allele length variations between individuals. The male-specific DYS391 gene is also included to detect Amelogenin null Y allele findings.