Searching for Unrelated Hematopoietic Cells

The search for hematopoietic cells begins with human leukocyte antigen (HLA) tissue typing the patient and the patient’s immediate family to assess the possibility of a related donor (related allogeneic transplant).

For 7 out of 10 patients, an unrelated donor or cord blood unit will be needed.  Physicians and transplant centers can search nearly 7 million potential donors and cord blood units that are available through the National Marrow Donor Program (NMDP) Registry.

When an unrelated allogeneic transplant is needed, the search process can be complex. It can take weeks or months to a find closely matched unrelated donor or cord blood unit due to factors concerning the patient, HLA typing and cell source.

A high degree of HLA matching between an unrelated donor and patient has been shown to:

• Improve overall patient survival
• Reduce post-transplant side-effects (such as graft-versus-host disease or GVHD)
• Improve the rate of engraftment (when the donated hematopoietic cells grow and re-generate new blood-forming cells)
  
  

Searching for an unrelated donor or cord blood unit

First, a preliminary search

• Why a preliminary search is performed: To find potential matches for the patient, assess the possible challenges in identifying closely matched hematopoietic cells and help shape a treatment plan for the patient.
• Who can request it: Any physician can request a preliminary search, any number of times, at no cost.
  
  

Then, a formal search

Additional HLA testing is needed to:

• Determine if the potential donors or cord blood units are matched at the level of resolution and at the HLA antigens required by the transplant center’s protocol
• Confirm the original HLA tissue typing

After a formal search is begun, the NMDP Registry is continually searched for added donors and cord blood units or those whose HLA information has been updated. If a new, potential match is found, the transplant center is alerted automatically.

• Why a formal search is performed: To find the best HLA match for the patient in time for transplant.
• Who requests it: Only a transplant center can request a formal search.

The transplant center selects the best cells for the patient.

Factors affecting the amount of time to find unrelated hematopoietic cells

Patient

• When transplant becomes an appropriate treatment, based on the disease, disease stage and patient's health.
• Urgency of the patient’s condition.

HLA typing

• Quality of the patient’s initial HLA typing. High resolution testing provides the information needed for an efficient search.
• HLA challenges of the patient’s tissue type and the search strategy for requesting further donor testing.

Cell source

• Whether cord blood is an option. (A cord blood unit is already collected and available for transplant when it is listed on the NMDP Registry; however, urgency is only one factor the physician considers when determining the best cell source for the patient.)
• Scheduling of donor appointments for testing, education and physical exams.
• Donors who are either permanently or temporarily unavailable. (Although most donors on the Registry are committed to donating, their participation is voluntary. Donors may be unavailable due to changes in health or personal situation, changes of heart about their commitment or changes in address that have made them difficult to locate.)
  

Procuring unrelated hematopoietic cells

• From a cord blood unit, the cells are requested from the cord blood bank and undergo confirmatory typing.
• From a donor, the workup begins. The donor attends an informational session, signs an informed consent agreement and provides a fresh blood sample for more testing. After the NMDP and the transplant center have completed testing to help ensure the safety of both the donor and the patient, the marrow or PBSC is collected.