Testing Used to Determine Marrow Donor Compatibility
There are six tissue antigens that must match very closely, if not exactly, in order for a potential donor to be compatible to donate. These antigens occur in our population in different frequencies. A patient with a more common "tissue type" is easier to match than if a patient with a combination of one or more rare antigens.
The characteristics of stem cells are inherited in the same way as hair and eye color. Therefore, the best chance of finding a donor match is from someone of the same racial or ethnic background.
Your blood type (a typing of the red blood cells) does not have any bearing on your HLA, or tissue type (a typing of the white blood cells and tissue cells.)
1. Preliminary Buccal Swab Testing
When you first register with the Be The Match Registry, an initial tissue type is performed on your cheek cells through a buccal or "cheek" swab. This tissue type is then entered into the National Marrow Donor Program Registry where it is compared to the tissue typing of each patient searching for a donor.
2. Early Matching
If you're identified as a possible or preliminary match, the Donor Center will contact you and answer any questions you may have.
You may be asked for another cheek swab if you registered many years ago or if a higher level of testing needs to be performed. Your will also be asked to complete a health history questionnaire to assess your current overall health.
3. Confirmatory Typing
If you have a complete, high resolution typing available, the National Marrow Donor Program will request confirmatory typing. A potential donor identified at this stage usually has five or six markers matching the patient needing a transplant. This means you are a very close match and could be a possible donor. You may be one of only a few donors matching this patient or one of several.
The Donor Center search coordinator will contact you to discuss what it means to be a match, answer any questions you may have, make sure you are still in good medical condition and schedule additional blood testing. Several tubes of blood will be drawn and sent to the transplant center to be tested in conjunction with the patient's blood. Results of the blood tests usually take about six weeks but can take up to several months.
This is the final stage of the matching process that occurs after you completed the confirmatory typing process. A donor "at workup" has been identified as a match! The Donor Center will contact you to schedule an information session to explain the procedure and answer all of your questions. If you choose to proceed to donation, you will receive a complete physical exam.
For more information about the testing process to determining a marrow donor match, visit the National Marrow Donor Program website.