When we started our blog we at Kashi Clinical Labs decided that we needed to keep it simple. When our family went through my daughter’s transplant so many times someone would come in and say something and we had no idea what they meant. Because Kashi’s private HLA testing website deals specifically with HLA testing I thought we might start with, WHAT IS HLA TESTING?
I thought that I would just give you a “street level” non-clinical definition of HLA testing. HLA testing is a complex form of testing that doctors use to see if there is a compatible donor for a patient in need.
Human Leukocyte Antigens, HLA are protein molecules that we inherit from our parents. Thousands of different HLA molecules have been identified, and matching essential HLA types is critical to the potential success of a transplant.
The HLA "match" is the number of HLA molecules that any two people have in common. HLA matching is usually based on ten HLA molecules. The more molecules two people share, the better the match. That is, their immune systems are less likely to see each other as "foreign" and are therefore also less likely to attack each other.
The most likely place to find an HLA match between two people is among siblings (that is, a brother or sister who share the same parents). If siblings inherit the same HLA molecules from both parents as the patient, they are said to be an "HLA identical match."
There is a 25% or one in four chance of being an identical match with a sibling. If no sibling match is found, doctors will frequently ask additional blood-related family members to be tested. These are usually aunts, uncles, cousins and grandparents.
However, two unrelated people can also be a good HLA match. Although it is less likely, it is possible that you could have some of the same HLA molecules as a friend or someone you don't even know. If you and the patient share three HLA molecules, for example, then you are said to be a "three HLA antigen match.
In our next blog I will be talking about the “Search” process, followed by why it is important to have as close of HLA match as possible.