How Organ Matching Works

Organ matching for transplants is a complicated process of testing, made even more complex by the emotional outcomes of saving lives. Since there are more people needing organ transplants than there are donors at any given time. UNOS (United Network for Organ Sharing) was created UNOS uses strong policies and a digital network to use objective medical data to give patients the best opportunity for long-term survival.

When an organ becomes available for transplant, there are some logistical considerations such as location, condition and age or size. As time is a factor, organ donors and recipients that are physically far apart might not be a viable option.  Certain medical conditions or medications could make a donor organ of certain types less desirable for some patients. While age isn’t as much of an issue, the size of the organs to matter. Placing a full-size adult heart into an infant, for example, does not have the best outcome.

The main criteria for matching a living or deceased organ donor to a patient needing a transplant, however, is a set of medical blood and tissue tests. These include; blood type, tissue matching, and cross matching. While it’s possible for organs to be transplanted that do fully match, this process is about finding the highest possible compatibility so that the organ has less chance of being rejected after transplant.

Blood Type Matching For Organ Compatibility

Many people know their blood type, typically from donating blood, but few know what their blood type actually means. Each blood type relates to the type of glycoproteins (sugar and proteins) on the surface of the blood cells. There are two types of glycoproteins we refer to them as Type A and Type B. Your body naturally has antibodies for the type of glycoproteins you do not possess which means your body would attack these glycoproteins if introduced to your bloodstream. This is why a person who has Blood Type A cannot donate blood for a transfusion to a person with Blood Type B. People who have blood type AB have both glycoproteins and people with Type O blood have neither one.

People lucky enough to have type AB blood can get blood or organ donations from anyone, making them a universal recipient. People with Blood Type O can give blood or organs to anyone, making them a universal donor. The RH factor of the blood (positive and negative) do not impact organ donation.

Tissue Matching For Organ Compatibility

Tissue matching is a complex process involving testing the similarity of certain proteins, called antigens, between the donor and recipient. The more antigens two people have in common, the better outcome you can expect. If the tissue of the donor does not have enough commonality to the transplant recipient then the organ could be rejected and the whole process would need to start again, if possible. Patients can have multiple organ transplants but this is very hard on the body and the chance of long term success diminishes with each attempt.

Crossmatching For Organ Compatibility

The final test is the most complex and the most recently discovered tool for organ matching, which has dramatically increased the number of successful organ transplants. The test looks for pre-existing naturally occurring antibodies that make two people non-compatible for transplant. A test combing the liquid blood of the recipient’s blood with cells from the donor. If the cells are destroyed, there is a presence of non-comparable antibodies. A donation between these two would be very likely to cause organ rejection. A recipient can have antibodies from pregnancy, blood transfusions or prior transplants. This final test often determines for sure if an organ transplant is possible between the donor and recipient.

The three tests combined with the before-mentioned factors like organ size and location helps make UNOS decisions for matching recipients with deceased organ donors. Some organ types (such as kidneys) can be done with a living donor and these people are often related or friends with the person they are attempting to donate to. However, even two people that are related might not be a match for each other. Hospitals have attempted to get creative, by linking up sets of people that are not compatible with their donors in a domino-effect like multi-transplant procedure. For example. Your mother wants to donate a kidney to you but she is not a match. The hospital knows of another such couple who do not match each other but are a match for you. The organs are essentially traded between the two couples.

Other creative approaches include trying to rid the body of antibodies before the transplant. New procedures and tests are being developed all the time.