Matching kidneys for organ donation is a complicated process.
Kidneys are matched based on blood type. The process of matching blood donor blood types with your blood type is known as “cross-matching”. The following chart shows which blood groups match (are compatible). If you have a living donor, but that person’s kidney is not a match for you, you can still have a living donor kidney transplant. If your blood type doesn’t match the donor’s blood type, you will not be able to get a kidney from that person directly but you still may be able to receive a kidney transplant from another donor through the Kidney Paired Donation.
Your Blood Type
Receive a Kidney from Blood Type
|| A or O
|| B or O
|| AB, A, B, O
If a match is found from a deceased donor, it will likely be from a person with your blood type.
Being a compatible blood group is only one part of knowing if a person will be a match. You can still donate your organs even if you don’t belong to a compatible blood group. Rh factor is not important for kidney matching.
In Canada, the following percentages make up each of the 4 blood groups. Type O is the most common and type AB is the least common.
- type O – 46%
- type A – 42%
- type B – 9%
- type AB – 3%
How donors are matched
Your immune system protects your body against anything that doesn’t belong to you, like a cold or flu virus. Your body will attack the virus and try to destroy it by making antibodies against the virus. These antibodies stay in your body so the next time that same virus attacks, your immune system will remember the virus and make more of these antibodies to start an attack against it. This means your immune system gets ‘sensitized’ to those viruses.
Your body can also make antibodies against blood or tissue from a blood transfusion, organ transplant, or from being pregnant. A kidney won’t be a match if your body makes antibodies against the donor’s kidney.
For an organ transplant to work, you will need to have human leukocyte antigen (HLA) testing. This test shows if your body will make antibodies against the donor’s HLAs. If your body makes antibodies against the donor’s HLAs, it will likely attack the transplanted kidney and reject it. This is called being sensitized.
You will have blood tests to measure how many different HLA antibodies you have in your blood. In general, the higher number of HLA antibodies in your blood, the harder it will be to find a donor kidney that your body won’t reject.
Calculated panel reactive antibody
The calculated panel reactive antibody (cPRA) is calculation to find out what percentage of people are unlikely to find a potential match. The cPRA is based on the number of HLA antibodies that you have and is given as a percentage. For example, someone with a cPRA of 80% has HLA antibodies against 80 out of 100 potential donors. This means that they won’t match 80% of potential living donors and will likely have to wait longer to find a match.
People with a cPRA higher than 95% are called highly sensitized. They have a much harder time finding a match so they can register in the Canadian Blood Services’ Highly Sensitized Patient Program. This program aims to match people to donors who have passed away (called deceased donors) from across the country.