Richmond, Va. -- The OPTN/UNOS Board of Directors, at its meeting June 19 and 20, approved elements of a pilot national system to facilitate kidney paired donation. Kidney paired donation involves two or more living donor transplants where the initially intended donor/recipient pairs are medically incompatible; two or more donor/recipient pairs are then crossed to provide a compatible living donor for each recipient.
"The broader the base of people who can be matched, the more paired transplants can be done to help those in need," said Timothy L. Pruett, M.D., president of the OPTN and UNOS and chair of the OPTN/UNOS Board of Directors. "It's important to have a program that gives people the most opportunities possible for a transplant." The Board's action followed the December 2007 passage of the Charlie W. Norwood Living Organ Donation Act, which clarified the legal basis for paired donation.
The initial pilot system will be voluntary, open to any living donor kidney transplant program meeting OPTN requirements and for any candidate on the OPTN kidney waiting list. The matching system is designed to optimize the number of living donor kidney transplants through two-or three-way kidney exchanges, while allowing flexibility for circumstances such as the donor and/or candidate's willingness to travel for a transplant. Additional proposals for system improvement, such as ongoing "donor chains," will be considered as future results of the pilot are evaluated.
Since 2000, approximately 350 paired donation transplants have been performed in the United States. Potentially thousands more transplants can be done through paired donation. Several multi-center or regional networks currently arrange paired donation. The OPTN pilot program is not intended to replace these efforts, but to offer a program based on its existing data infrastructure and give programs and candidates potential national access in donor matching.
The Board also accepted a series of policy changes intended to help achieve the ultimate goal of eliminating deaths among children awaiting transplantation. The policy changes in general will ensure broader consideration of pediatric candidates, particularly when the organ donor is also a child or adolescent.
"The majority of organs from young pediatric donors already go to children," said Stuart Sweet, M.D., Ph.D., chair of the OPTN/UNOS Pediatric Transplantation Committee. "However, altering the sequence of offers will allow more efficient matching for children who are in need and may be at hospitals somewhat farther from the donor's location."
Specific policy changes include the following:
- In heart transplantation, existing preferential matches from adolescent donors (older than 11 and younger than 18) for pediatric candidates will be extended to all pediatric donors (less than 18). In addition, hearts from pediatric donors will first be offered to matching pediatric candidates up to 500 miles from the donor location for the most urgent patient category (Status 1A) before local adult Status 1A candidates. Status 1B pediatric candidates up to 500 miles from the donor hospital will then be considered for any offers not accepted for a 1A patient.
- In lung transplantation, a new Status 1 and 2 will be created for candidates age newborn to 11. Previously, these candidates received priority for lung offers based only upon occrued waiting time. Status 1, the most urgent, includes patients who meet criteria indicating they have respiratory failure or severe pulmonary hypertension. Status 1 candidates will receive higher transplant priority than Status 2. In addition, lungs from deceased donors age 11 or younger will be offered to all compatible candidates 11 or younger within 1000 miles of the donor location before other patients are considered.
- In liver and combined liver-intestine transplantation, organs from donors age 10 or younger will first be considered for all Status 1A (most urgent) local and regional pediatric candidates (younger than 18), then all national Status 1A candidates age 11 and younger, before the organs are considered for other candidates.
In other action, the Board approved a proposal to increase efficiency in kidney matching by focusing mandatory regional and national sharing of zero-antigen mismatched kidneys for adult candidates who are harder to match because of their highly sensitized immune response. A zero-antigen mismatch occurs when the donor and potential recipient show no differences on any of six key immune system markers associated with the best long-term kidney survival. About 14 percent of all deceased donor kidney transplants currently occur as a result of zero-antigen mismatches.
Kidney candidates' overall immune sensitivity is measured by a calculated panel reactive antibody test (CPRA). This test gives a percentage of antigens (immune system markers) that might lead to early organ failure if the patient receives a kidney with that specific antigen.
Candidates with a CPRA of 20 percent or less are likely to have very few incompatible antigens with donor kidneys. As such, their likelihood of long-term success is not as dependent on getting a zero-antigen mismatch as candidates with a higher degree of sensitivity, and their likelihood of getting a compatible match is higher than that of people with high CPRA scores. The OPTN/UNOS Kidney Transplantation Committee found that mandatory shares beyond the local allocation area for low-sensitivity candidates created logistical inefficiencies and tended to benefit Caucasian patients more than candidates of other ethnic backgrounds.
Mandatory sharing will continue at the regional and national levels for zero-antigen mismatches for adult candidates whose CPRA is higher than 20 percent, and for any pediatric zero-antigen mismatched candidate regardless of CPRA. In addition, local zero-antigen mismatched candidates will have the highest priority regardless of the candidate's CPRA.
The Organ Procurement and Transplantation Network (OPTN) is operated under contract with the U.S. Department of Health and Human Services, Health Resources and Services Administration, Division of Transplantation by the United Network for Organ Sharing (UNOS). The OPTN brings together medical professionals, transplant recipients and donor families to develop organ transplantation policy.