Kidney paired donation (KPD), or paired exchange, is an approach to living donor kidney transplantation where patients with incompatible donors swap kidneys to receive a compatible kidney. KPD is used in situations where a potential donor is incompatible. Because better donor HLA and age matching are correlated with lower lifetime mortality and longer lasting kidney transplants, many compatible pairs are also participating in swaps to find better matched kidneys. In the United States, the National Kidney Registry organizes the majority of U.S. KPD transplants, including the largest swaps. The first large swap was a 60 participant chain in 2012 that appeared on the front page of the New York Times and the second, even larger swap, included 70 participants and was completed in 2014. Other KPD programs in the U.S. include the UNOS program, which was launched in 2010 and completed its 100th KPD transplant in 2014, and the Alliance for Paired Donation. According to a 2019 study, kidney exchanges improve overall transplant quality, which leads to fewer transplant failures. The exchanges also reduce waiting times for patients needing kidney transplants. The study found that the health care cost savings of kidney exchanges are substantial.
Types of swaps Swaps of kidneys come in two distinct types: cycles and chains. Cycles only include donors who are paired with a patient so that the donor donates a kidney only if their patient receives a kidney in the swap. Chains are initiated by non-directed donors. These donors, also known as unpaired or altruistic donors, donate a kidney without any expectation of a reciprocal kidney donation to any specific patient.
Reasons More than one-third of potential living kidney donors who want to donate their kidney to a friend or family member cannot donate due to blood type or antibody incompatibility. Historically, these donors would be turned away and the patient would lose the opportunity to receive a life-saving transplant. KPD overcomes donor–recipient incompatibility by swapping kidneys between multiple donor–recipient pairs. KPD is also being used to find better donor–recipient matches for compatible pairs who want a lower lifetime mortality and longer lasting transplant.
History
Early days The first paper outlining the concept of paired exchange was authored by FT Rapaport and published in 1986. The first recorded paired exchange transplants were organized in South Korea by Dr. Park beginning in 1991. For nearly a decade, only Park and his team in South Korea utilized this novel approach to facilitate transplants for incompatible donor–recipient pairs. In 1999, the first KPD transplants were performed in Europe followed by the first KPD transplants in the United States in 2000. Over the next ten years the United States would become the most competitive KPD market in the world with more than a dozen KPD programs commencing operations and many KPD programs failing. Outside of the United States, most of the KPD programs have been organized or sponsored by governments which has limited innovation in these programs. Three of the important early KPD programs in the U.S. were the Hopkins program led by Dr. Montgomery and Dr. Segev, the New England Paired Kidney Exchange (NEPKE) led by Dr. Delmonico and Professor Alvin Roth and the Ohio Organ Consortium which later reorganized as two competing programs, the Paired Donation Network (PDN) led by Dr. Woodle and the Alliance for Paired Exchange (APD) led by Dr. Rees. The Hopkins program, which was based out of the Johns Hopkins Hospital, led the industry in early innovations including the critical "domino chain" breakthrough which allowed Good Samaritan donors to start chains, dramatically increasing the number of pairs that could be matched in a swap compared to the loop approach that was used previously. Once the Hopkins team began organizing Domino Chains, these swaps became larger and began attracting national media attention due to the massive complexity and significant impact of these large swaps. Unlike the Hopkins program that was hospital based, NEPKE was launched within the New England Organ Procurement Organization which served several states in the North East. The PDN and APD organizations were founded by transplant surgeons but attempted to create networks of transplant centers that would work together to pool their incompatible pairs, much like NEPKE but without OPO support. In 2006, the APD conceived of a critically important innovation called "NEAD Chains" that amplified the matching power of Domino Chains by allowing Bridge Donors to extend chains. Prior to the utilization of Bridge Donors, a chain of transplant surgeries would be completed in one day, which limited the number of transplants that could be performed. A bridge Donor is someone whose paired recipient has received a kidney but does not donate for some period of time (generally 1 week to 3 months). Just like Domino Chains increased KPD transplants, the utilization of bridge donors also dramatically increased KPD transplants because chains could now be organized over several months and avoid the logistical limitations of performing all surgeries on one day. In 2007, the APD completed the first NEAD chain. That same year, the U.S. Congress passed the Charlie Norwood Act which clarified that paired exchange was legal. Prior to the passage of this law, many in the U.S. transplant community feared that KPD was unlawful due to the prohibition of "valuable consideration" as articulated in the NOTA laws that govern the U.S. transplant industry. With the passage of the Charlie Norwood Act, many more KPD programs were launched in the U.S. including the UNOS KPD program which was government sponsored with funding from deceased donor registration fees and charitable contributions.
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