Matching Recipient and Donors
The terms “match”, “matching” or a “perfect match” are often misunderstood or misused when
referring to a recipient and donor.
A clearer way of describing the evaluation process between a recipient and donor would be to use
the terms, “suitable” and “compatible”. A suitable donor is someone that is healthy enough to
donate. A donor is compatible when all the tests are finalized and a suitable donor is able to donate
to their intended recipient.
The history of the term “match” comes from the 6 HLA antigens, (Human Leukocyte Antigens.) In the
past, the recipients and donors 6 antigens needed to “match” in order for that donor and recipient
transplant to be successful. The new anti rejection drugs are so effective, that there isn’t a statistical
difference in success rates between a zero “match” and a 5 out of 6 “match.” Therefore, HLA
matching typically is not a factor that determines whether someone is compatible. There is however,
a benefit to having a “perfect match,” 6 out of 6 antigens. A “perfect match” results in a significantly
longer survial of the donated kidney.
Donor/recipient compatibility is dependant on the following:
Blood Type Matching
Scientists have known for many years that blood group matching is important in transfusion and it is
equally important in kidney transplantation.
There are four major blood types. These types are simply noted as blood type A, B, AB and O. The
positive or negative feature in blood typing is not a factor when determining compatibility between a
donor and a recipient.
Blood Type Compatibility Chart
|Blood Type:||Can Donate To:|
|O||A,B, AB, O|
|A||A or AB (O)*|
|B||B or AB|
|Blood Type:||Can Receive From:|
|A||A or O|
|B||B or O|
|AB||A or B or AB or O|
|(Blood Type O is the Universal Donor: donors with O blood are compatible with any other blood type)|
|(Blood Type AB is the Universal Recipient: recipients with AB blood are compatible with any other blood type)|
|* Recently, it has been discovered that some donors with blood type A may donate to a blood type O recipient. Person with blood type A or AB and someone with blood type B may donate to a person with B or AB. A person with blood type AB may only donate to an individual who has that same blood type.|
PRA’s - Panel Reactive Antibodies
When it comes to pursuing a kidney transplant most people are thinking about finding a compatible
donor. They don’t realize that there is a test you need to take that will determine how easy or
difficult it will be to find that compatible person. The test is called PRA.
PRA’s, panel reactive antibodies is a blood test that measures the level of antibodies in the recipients
blood. The more antibiodies you have, the more difficult it will be to find a compatible donor. A
person's PRA can be anywhere from 0% to 99%. Your PRA represents the percent of the U.S.
population that the antibodies in your blood would react to and reject the kidney. For example,
having a PRA of 25 means that 25% of the population will not be able to donate a kidney to you. The
antibodies present in your blood would attack the transplanted kidney and can cause immediate
About 20% of the people who need a kidney transplant have high PRA’s. Simply stated, having a high
PRA will significantly limit the number of people that will be able to donate to you.
You can develop high PRA’s from a blood transfusion, an earlier transplant or for some women, from
There are ways of lowering PRA’s through a procedure called Plasmapheresis a blood-cleansing
process that can lower the dangerous antibodies from the blood. Plasmapheresis is usually used
when you have an incompatible living donor.
Plasmapheresis can also been used to allow blood-type incompatible donor/recipients to proceed
with the transplant. Plasmapheresis can cost tens of thousands of dollars and are complex to
If you’ve been told by a transplant center that you are too highly sensitized, (another term used to
describe high PRA's,) to receive a transplant ask about Plasmapheresis. If they don’t offer it there,
speak to another transplant center.
Cross matching is a very sensitive and final test performed on a kidney donor and a particular
recipient. Laboratory techniques for cross matching have been refined and now enable scientists and
physicians to define how a kidney transplant recipient may respond to particular cells or proteins of
the kidney donor. These refinements in testing have led to very accurate tests that were not available
even a few short years ago.
The basic cross match test involves a mixing of cells and serum to determine whether or not the
recipient of a kidney will respond to the transplanted organ by attempting to reject it. In recent years,
scientists have applied more intricate tests and obtained more accurate results of cross matching. It is
now possible to better indentify a recipient who might reject an organ and thus avoid a transplant
that might not succeed. Thus, improved kidney transplant outcomes may ensue because we can
better determine and predict how the recipient may respond to the donated organ. Cross match
testing, therefore, has evolved and improved long-term results.
Cross match testing, which involves several different phases and, as many as 10 to 15 different tests,
comes down to a fairly simple final result. Either the cross match is positive or negative. A positive
cross match means that the recipient has responded to the donor and that the transplant should not
be carried out. A negative cross match means that the recipient has not responded to the donor and
therefore transplantation should be safe. A positive cross match (not what you want,) essentially says
that the recipient will respond to the donor organ by rejecting it and the operation should not be
performed. A negative cross match says to the recipient, you are not likely to reject the donor organ
and the operation should be performed. If we look at the cross match in this way, the positive and
negative results make sense to all concerned.
A well matched kidney is one in which the blood type between the donor and recipient are
compatible, the tissue typing well defined and hopefully well matched and all cross match studies are
negative. Application of good matching studies in clinical kidney transplantation has allowed for
excellent results using living donor and deceased donor organs and has permitted safe kidney
transplantation for thousands of patients with end-stage renal failure.