Why is so much blood required for HLA testing?
HLA typings are now performed using molecular methods, which mean that a typing can be completed using less blood from the patient. However, crossmatch techniques still require that live lymphocytes, a specific type of white blood cells, be isolated from the peripheral blood. The ratio of red blood cells to white blood cells is about 1000:1. Therefore, we need to be able to start with enough whole blood to isolate lymphocytes to complete the testing. Lymphocytes are also used for preliminary and final crossmatches. If extra cells can be isolated, they will be frozen and saved in case they are needed in the future.
Why do I send in a blood sample every month?
One of the requirements for being on the waiting list for a deceased donor kidney transplant is to submit samples monthly. These samples are screened periodically to determine if there are anti-HLA antibodies present in the serum or the liquid portion of the blood.
How long will I be on the waiting list before I am offered a kidney?
Unfortunately there is no simple answer to this. Waiting time for a deceased donor kidney transplant can vary dramatically from person to person. For more information on organ allocation contact your transplant coordinator or see the United Network for Organ Sharing (UNOS) website.
How long does the final crossmatch take when I am offered a kidney?
When the transplant program accepts a deceased donor kidney offer for a patient, the HLA lab performs the final crossmatch prior to transplant. This is considered STAT testing and the HLA technologist on-call will perform the crossmatch at any time of the day or night. This testing can take up to 6 hours from the time the samples are received to the time the transplant program is notified of the results.
What is a PRA?
PRA stands for Percent (or Panel) Reactive Antibody. The PRA is expressed as a percentage and is used as a rough estimate of what percent of donors a person will NOT be compatible with. In other words, a person with a PRA of 40% will NOT be compatible with roughly 40% of possible donors.
Can my PRA change?
Yes. Typically a PRA is highest following a sensitizing event (pregnancy, transfusion, or transplant) and decreases with time. Patients who are not sensitized should consistently have a PRA of 0%
If I have not had a sensitizing event, do I still need to send in my monthly blood sample?
Yes. It is an ASHI requirement to collect samples monthly on all kidney transplant candidates. In addition to antibody screening, these samples may be used for a final crossmatch in some cases.
If I am the same ABO type as my sibling, does this mean we will have the same HLA type?
No. Although the genes that code for the various HLA antigens are inherited together, the genes that code for your ABO type are not inherited with your HLA antigens.
What are the chances of being a match with my immediate family?
An individual will inherit half of their HLA antigens (called a haplotype) from each of their biological parents. If the parents share any HLA antigens with each other, it is possible for their child to share more than 3 antigens with the parents. For siblings, there is a 1 in 4 chance of being HLA identical, a 1 in 4 chance of being completely non-identical, and a 1 in 2 chance of sharing a haplotype.
What are the chances of being a match with more distant relatives or friends?
The likelihood of being HLA identical gets lower for more distant relatives. A first cousin has a 1 in 16 chance of being HLA identical. The chances of being a match with unrelated individuals depend on the frequency of your HLA antigens in the population.