ABO Incompatible Kidney Transplantation – A Solution to a Growing Need

by Lesley Kresie, MD

The number of patients requiring a kidney transplant continues to rise each year and the number of organ donors remains insufficient to meet the need. The growing list of patients waiting for an organ has led transplant programs to look at all possible donor options for their patients, such as living donors, paired donors and, more recently, incompatible donors. The improvements in immunosuppression regimens have created an opportunity to decrease the wait time for patients on the transplant list by offering organs that would have previously been considered incompatible. Major ABO incompatibility (e.g. group A1 donor to group O recipient) still requires intense evaluation and desensitization prior to transplant; however, these transplants have been done successfully with long-term outcome rates similar to ABO compatible pairs, and the numbers will continue to rise.

Use of major ABOi kidneys is generally only performed in the living donor setting and, therefore, will not address the needs of patients on the wait-list for a deceased donor. When a deceased donor’s organ becomes available, there is not enough time for a patient to undergo extensive desensitization prior to transplant, so the risk of acute rejection is very high with an ABO incompatible donor. However, not all ABO group A donors are type A1. The qualitative and quantitative differences in antigen expression, between blood group A1 versus non-A1, has allowed transplant programs to consider these organs in the deceased donor setting without the need of extensive pre-transplant desensitization.

All group A and AB deceased donors are now typed for the presence of the A1 antigen. If negative, the non-A1 (or non-A1B) donors are offered to group B patients, as this group has the longest waiting time on the transplant list of any blood group. Several transplant programs have been performing the non-A1 to B transplants for decades with great success. In order to extend this practice to other programs, the Organ Procurement and Transplantation Network updated their policies in December 2014 to allow all transplant programs to transplant non-A1 and non-A1B kidneys to group B patients without requiring a variance. In order for the patient to be listed as eligible, the transplant program must have written informed consent that the patient is willing to accept the non-A1, non-A1B kidney. The program must also establish a written policy regarding acceptable antibody titer threshold in the patient for receiving these organs and must confirm the candidate’s eligibility every 90 days (+/- 20 days).

One of the biggest obstacles for transplant programs in implementing this new opportunity has been determining antibody titer threshold and patient eligibility. This process will require close communication with the transfusion service so that all parties understand, and agree on, the methodology, frequency of testing, and titer threshold for a successful transplant. For additional information, please visit: https://optn.transplant.hrsa.gov/media/2347/mac_guidance_201712.pdf