Last week I had the privilege of meeting with Rhonda Holdsworth, Lab Director (Science and Operations Manager) at the Australian Red Cross Blood Service at Southbank in Melbourne.
Rhonda very generously set aside time to explain the Red Cross Blood Service’s role in screening donor kidneys (and other organs) for transplantation.
Firstly, the procedures, tests, and crossmatching techniques are not unique to Melbourne or Australia. Blood services worldwide share techniques, advances, and breakthroughs uninhibited by patents, copyright or any other legal or informal restraint. This approach, which is rare in the competitive world of medical research, ensures that blood services large and small provide a consistent, world-class service to the citizens of each country.
For kidney transplants, there are two kinds of donations, living and deceased. Fortunately or otherwise, I have experience both types. My wife gave me a kidney in 1996 and I received a kidney from a deceased donor in 2005.
The workup for either type begins at the Transplant Clinic, where you first nominate to be placed on the transplant list. Before my first transplant, this seemed a no-brainer. After all, who wouldn’t want to escape from dialysis? However as I have become older and wiser, I have found several reasons. Some people refuse to be on the list for what they see as ethical reasons. Others, like me, have had bad experiences with transplants and are very wary of going through another. Still others may consider themselves too old and are quite happy being on dialysis.
Once you make the decision, the main game is with the Blood Service. They test your blood for a range of factors: blood group, DNA, and a range of antigens and antibodies in the HLA (human leukocyte antigen) system. An antigen is a molecule recognized by the immune system. Your HLA antigens are usually tolerated by your immune system, whereas foreign antigens are identified as intruders and attacked by the immune system. They also screen for Hepatitis and HIV.
Once these (and other) tests are complete, your details are registered in NOMS, the National Organ Matching System (in Australia): the “Waiting List”.
As some antibodies can change over time, everyone on the list must provide a new blood sample each month for testing. These samples are usually cross-checked multiple times by labs in other states.
As soon as a kidney becomes available, the top 20 candidate recipients are matched by the NOMS computer. The matching is a combination of points (HLA, etc) waiting time and antibody profile. Typically if two kidneys are available, one is allotted to the best match nationally, the other to the best match in the donor’s home state.
The blood Service then performs the donor and recipient matching process, which involves three stages: blood type matching, tissue type matching and crossmatching. Each of these applies to both living and deceased kidney donations.
Blood type matching. There are four major blood types in humans, noted as blood type A, B, AB and O. A recipient with blood type O can receive a kidney only from a donor with blood type O. A recipient with blood type A may receive a kidney from a recipient with blood type O or A and a recipient with blood type B can receive a kidney from a donor with blood type O or B. Finally, a recipient with blood type AB can receive a kidney from a person of any blood type.
Tissue matching relates to genetic (antigen) matching between donors and recipients. There are typically at least six specific antigens in each donor and recipient. The best compatibility is a six-antigen match between a donor and a recipient. This match, which occurs 25 percent of the time between siblings (brothers – sisters) having the same mother and father, also occurs from time-to-time in a random fashion in the general population. This is the single best tissue match that can occur between any donor and recipient.
Crossmatching is a very sensitive and final test performed on a donor kidney and a particular recipient. The basic crossmatch test involves a mixing of cells and blood serum to determine whether the recipient of a kidney will respond to the transplanted organ by attempting to reject it.
Crossmatching involves several different phases and as many as 10 to 15 different or separate tests, comes down to a fairly simple final result. A positive crossmatch means that the recipient has responded to the donor and that the transplant should not be carried out. A negative crossmatch means that the recipient has not responded to the donor and therefore transplantation should be safe.
As you can imagine, these tests are both sensitive and time-consuming. Most are done by hand. Where a transplant involves a deceased donor, testing begins as soon as possible and typically lasts 8 to 10 hours, with two lab staff cross-checking each other’s work.
On completion of testing, the best four matching recipients are identified. The first on the list is offered the kidney, and if they refuse it, the second and so on in turn. I have experienced this phone call (just before going to a movie), and it is a real buzz!
I had little idea of the work done behind the scenes by so many people over months or even years, with one aim in mind: a successful transplant every time. Thank you Rhonda and thanks to your team. Without you we wouldn’t get to first base.