The Donation Process: Stages of Matching

How Stem Cells Work

When you first register with the National Marrow Donor Program Registry, an initial "tissue type" is performed on your cheek cells. This identifies the first four of the six antigens that are needed to be a stem cell match.  

This tissue type is then entered into the NMDP Registry where it is compared to the tissue typing of each patient searching for a donor.

Antigens are proteins found on the surface of the white blood cells and other body tissues.  These  particular antigens are named HLA-A, HLA-B and HLA-DR.

Stem Cells are manufactured in the bone marrow. They form the white blood cells, red blood cells and platelets in our blood.  These are the cells that are transplanted into patients in a marrow transplant.

This means the first four tissue antigens preliminarily match a donor to a patient needing a marrow transplant. The Transplant Center (where the patient is) asks the Donor Center to request a specimen from the donor for "DR testing."

The Donor Center contacts the potential donor to tell them they are a preliminary match, answers any questions they may have, and makes sure they are still interested in being on the Registry.

The HLA-DR type is then performed on the potential donor's cheek cell sample to identify these last two markers needed for a complete tissue type. This test usually takes about two weeks, but can occasionally take much longer. 

This stage is skipped for donors who already have their DR type in the registry (see "Ways You Can Help".)

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A potential donor identified at this stage usually has five or six markers matching the patient needing a transplant. This means they are a very close match and could be a possible donor. They may be one of only a few donors matching this patient, or one of several.

The Donor Center coordinator contacts the donor to discuss what it means to be a match, answer any questions the donor might have, make sure the donor is still in good medical condition and eligible to be a donor and schedules additional blood testing. 

Several tubes of blood are drawn from the potential donor 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 several months.

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This is the final stage of the matching process. A donor "at workup" has been identified as a match!

The Donor Center contacts the potential donor to schedule an information session with the donor, family members, the medical director and the Donor Center coordinator. This information session takes about an hour and a half.

The transplant center where the patient is located will request that a donor consider one of two types of stem cell collections – marrow collection or peripheral blood stem cell (PBSC) donation. 

• Marrow Collection: For marrow collection, a needle is placed into the iliac crest of the pelvic bone and the bone marrow is removed by a syringe. This is performed in day surgery under anesthesia, so the procedure is not painful for the donor. Most donors do experience some soreness in the hip for several days following the procedure.

• PBSC Collection: For a peripheral blood stem cell (PBSC) collection, the donor is given one injection of a protein called filgrastim each day for five days. This increases the number of stem cells released from the bone marrow into the blood stream. On the fifth and sixth day, the donor's stem cells are collected by a procedure called apheresis. During apheresis, the donor's blood is removed through a sterile tube and passes through an apheresis machine that separates out the stem cells. Remaining blood, minus the stem cells, is returned to the donor in another sterile tube placed into the other arm.

If the potential donor decides to continue, he or she is scheduled for a physical examination to make sure he or she is in good health and that the donation procedure will not be dangerous to him or her in any way. The donor is then asked to sign an "intent to donate," the patient is told they have a matched marrow donor, and the target date for a transplant is set.

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All of the stages of matching between a donor and a patient begin with first finding a potential donor listed on the registry. It is critically important that the Donor Center has an accurate address and phone number for all donors at all times. You may leave a change of address by voice mail 24 hours a day by calling toll free, 888-724-2811 or submit an online change of address.

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