You find someone you are interested in donating to, now what? Compatible pairs are based on several different factors. These include- compatible blood types, tissue (HLA) typing and crossmatching. Each of these are blood tests that will be completed to determine if the donor and recipient are a good enough ‘match’ to continue with the kidney transplant.
Compatible blood types
The first blood test done is to determine if there is a compatible blood type between the donor and recipient. O is the universal donor blood type, meaning a person with this blood type can donate to anyone, and AB is the universal recipient blood type, meaning a person with this blood type can receive a kidney from anyone. Reference the chart below to learn more about which blood types are compatible.
Tissue (HLA) Typing
This set of criteria for matching a donor and recipient are based on the number of antigens the donor and recipient share. Each person has six basic antigens (markers) shared equally from their parents. The more antigens that match between the donor and recipient, the better. A better HLA match is correlated with lower patient mortality over time because it reduces the number of antibodies created. The best match is for the recipient and donor to have six out of six antigen matches however it is not necessary in order to have a successful transplant.
Cross matching is done to ensure that the donor kidney will not be attacked by the recipient’s body once transplanted. Harmful antibodies in the recipient are more likely to attack a donor’s kidney if the recipient has had a previous transplant, pregnancy or a prior blood transfusion. When these antibodies are present, the recipient is known as being sensitized.
To test a recipient for these antibodies, a ‘crossmatch’ is done where a sample of the recipient’s blood is mixed with a sample of the donor’s blood. If the crossmatch is positive, it means the recipient’s antibodies attacked the donor’s. If it’s negative, it means the recipient’s antibodies did not attack the donor’s.
This is the final test to determine if the donor and recipient are a match and is a good indication if the recipient will reject the new kidney. This is the only test where a negative result is a good result!