The Network - Issue 1, Spring 2011
Closing the Gap
The Art of Finding a Needle in a Haystack
A look behind the scenes of OneMatch's search for a stem cell match
By: Michelle Venance, Search Analyst, One Match Stem Cell and Marrow Network (Ottawa)
The search analysts at OneMatch Stem Cell and Marrow Network know they have a great responsibility: to find a stem cell match for a patient who has reached their last hope for survival. When a match within the patient's family cannot be found, the search for an unrelated donor begins-and the search analysts are keenly aware time is of the essence.
Once a new patient is received at OneMatch, the search analysts begin their quest for an unrelated donor or umbilical cord blood unit by entering the patient's demographics and Human Leukocyte Antigens (HLA) typing into the OneMatch computer database. Stem cell donor and HLA matching are necessary for several reasons: to improve the success of a transplant, to promote engraftment or the growth of new cells, and to preventing transplant rejection (graft-versus-host disease-GVHD).
Human Leukocyte Antigens (HLA) is a type of protein found on the outer surfaces of cells. HLA protein is made up of six antigens, molecules that stimulate an immune response (i.e. help your body identify the cells that belong to your body from those that don't belong).
Using their many years of experience in HLA typing and matching, the search analysts at OneMatch check to ensure that the HLA typing entered is accurate. They liaise with the patient's Transplant Centre (TC), international registries and umbilical cord banks to be certain the search for a donor proceeds as smoothly and quickly as possible.
The Canadian donor base of more than 268,000 registrants is searched first, a process that takes the computer only minutes. When the search is completed, the analyst forwards a list of potentially suitable donors to the TC for consideration by the patient's transplant coordinators and physicians. This is usually done within 24 hours of OneMatch receiving the new patient.
Next, the analyst enters the patient's HLA-typing information into Bone Marrow Donors Worldwide (BMDW), an international database that currently stores HLA typings from more than 15 million donors and cord blood units. These typings come from 64 stem cell donor registries in 44 countries and from 44 umbilical cord blood banks in 26 countries. A list of potentially suitable donors is forwarded to the TC for its consideration. Searches of international registries are then requested based on where the best-matched potential donors are located. Once received by the analyst, this information is also forwarded to the TC.
If the patient has a common HLA typing, many donor options will exist and the TC will have no difficulties in selecting a suitable donor. Most donors require further typing to ensure they are fully matched before they are selected. This additional typing can take up to several months to complete.
Unfortunately, many patients have difficult searches where no obviously suitable donors are identified. In this case, the TC may request additional assistance from the OneMatch analyst who will then complete a detailed review of the patient's search prospects. The analyst will identify those aspects of the HLA typing that are causing difficulties and offer suggestions for further typings of donors as well as the best options for mismatched donors and cords.
Certainly, the personal connection for the search analyst is doing everything in ones power to find 'the needle in the haystack' When the difficult searches get resolved, you know you have done your job to the best of your ability. And that is a great feeling.