ESSENTIAL BLOOD TESTS PRIOR TO A TRANSPLANT
Three blood tests are done sequentially during the transplant work up to determine if the potential donor is a match. These tests are:
1) Blood typing (ABO compatibility)
2) Tissue typing (HLA typing)
3) Cross match
This is the first test performed to see if the blood groups between the donor and the recipient are a match.
There are 4 blood groups – A, B, O and AB.
Blood group O is the “universal donor” which means he can donate to any of the four blood group recipients.
Blood group AB is the “universal recipient” and can receive from any of the four blood groups.
In short, then:
a) blood group O, can receive from blood group O only
b) blood group A, can receive from blood groups A and O
c) blood group B, can receive from blood groups B and O
d) blood group AB, can receive from blood groups A, B , O and AB
TISSUE TYPING (HLA TYPING)
Once it is determined that the blood groups between the donor and recipient are a match, tissue typing or HLA typing is done to see how well they match.
HLA stands for Human Leukocyte Antigen. HLA are proteins that are located on the surface of the white blood cells and other tissues of the body.
When two people share the same HLA, their tissues are immunologically compatible with each other. The better the HLA match, the longer a transplant will last, generally speaking.
There are three general groups of HLA – HLA-A, HLA-B and HLA-DR.
Each person has 2 sets of HLA in their cells.
Each child inherits one set of HLA from each parent. Therefore, there is a 1 in 4 chance of being an identical match with the siblings.
This test looks for antibodies that a recipient might have to a specific donor.
Antibodies are proteins that look for “foreign cells” and can attack the HLA of the donor, if they are specific to the donor. This causes the recipient to reject the organ.
Crossmatch is performed by mixing a sample of the recipient’s serum to the white blood cells of the donor. If the antibody is present in the recipient’s blood to the donor HLA, it will be read as a “positive” crossmatch, which means that the transplant should not be performed with this specific donor’s organ. A ”negative” crossmatch means that there are no antibodies specific to the donor and therefore, the transplant can proceed.