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It’s a Match!

Now that I’ve got your attention, no, this article isn’t a guide on how to craft the perfect Tinder profile. I assure you, however, that you’ll have no trouble scoring a date with your knowledge of The United Network for Organ Sharing (UNOS). While the organization has been in operation since its establishment by the 1984 National Organ Transplantation Act, its heyday came in 2004 when economist Alvin Roth unveiled a revolutionary new approach to kidney allocation that would eventually win him the 2012 Nobel Prize in Economics. Kidneys are a unique entity in transplant medicine because each healthy person has two kidneys but only needs one to survive. This creates a potential supply of “extra kidneys,” and while technology can’t force a healthy person to give up one of their kidneys to someone in need, it can help allocate the supply that are available through cadavers and generous living donors. In 2003, 8,665 patients across the entire United States were able to receive a kidney transplant, almost all from deceased donors. By 2016, 19,061 patients per year received a live-saving kidney transplant in large part thanks to Roth and his contemporaries. This success, however, does not come without its fair share of challenges. The field of solid organ transplantation exists at the intersection of economics, genetics and ethics – with important moral implications of a system that aims to maintain fairness.

As medical students, we have a unique relationship with paired donor matching systems. It turns out that the process that matches patients with potential organ donors is based on the same underlying method used to match medical students with residency programs. The algorithm that now regulates, among other things, the allocation of solid organs, began as a thought experiment by labor economists aimed at designing a model to describe the establishment of mutually beneficial relationships – so-called “Matching Theory.” In the residency match, a system is created by which medical students are matched with the program they most prefer among programs which preferred them. Now substitute “preference” for “genetic compatibility” and, voila, you’ve taken a market economists’ approach to organ allocation.

Suppose two individuals, Bob and Amy, both require a kidney transplant and have family members willing to donate a kidney to them. Unfortunately, Bob’s wife, Sue, is not a compatible donor for him. Neither is Amy’s sister, Kim, a compatible donor for her. In the pre-Roth era, Bob and Amy would be stuck waiting for a deceased donor with less than a 40% chance of eventually receiving a transplant. Through the power of UNOS, however, we might discover that Kim is a compatible donor for Bob and that Sue is a compatible donor for Amy, allowing us to facilitate an even exchange of organs between the two pairs.

This example only scratches the surface of the system’s capabilities. The true power of UNOS is its ability to arrange higher order exchanges between pairs of three or more donors. In one such situation, a woman from North Carolina, in an act of pure altruism, offered to donate a kidney to any compatible recipient through UNOS. Her generous donation allowed the system to “unlock” a scenario in which her kidney would be donated to a woman in Minneapolis whose husband would then donate a kidney to a woman in Atlanta, thereby allowing two patients to receive kidneys who otherwise would not have been able to. She became what is known as a non-directed donor, and transplant physicians now refer to this kind of non-directed organ donation as a “Non-Simultaneous Extended Altruistic Donor” (NEAD) Chain. There are documented cases in which up to a nine-way exchange was facilitated as a result of a single donor via a NEAD chain.

Although this may seem like a win-win-win scenario for all parties involved, the ethical considerations of organ transplantation add another layer of complexity to the design of a paired donor system. At the crossroads of “supply and demand” and “life and death,” the goal of a fair and efficient “marketplace” for organs may be difficult to define. Despite the success of Alvin Roth’s approach, there are still over 120,000 patients waiting for a kidney transplant with the average waiting time estimated to be over three years. This is the unfortunate reality of transplant medicine in which approximately 13 patients die daily while waiting for a life-saving kidney transplant. So how do we, as physicians and as a society, decide who gets a kidney? And how do we decide who can donate (or sell) a kidney?

Feel like you’ve got a kidney burning a hole in your retroperitoneum? You’re out of luck. The same act of legislation that established UNOS in 1984 also prohibited the buying and selling of organs in the United States. Therefore, in theory, a wealthier person would not have any advantage in obtaining a donor organ over a less wealthy person. While this may sound fair, it also limits the supply of available organs by prohibiting an individual from being compensated for organ donation. This means that many living donors who might be willing to donate a kidney for a given price are unable to. This is one of many moral conundrums that comes with designing an organ allocation system. Do we increase the supply while creating an unfair advantage for wealthy patients, or do we maintain equal access while limiting supply?

Several alternatives have been suggested to incentivize non-directed donors without direct financial compensation, providing, for example, a lifetime tax exemption or some form of life insurance to an individual who is willing to donate a kidney to a non-relative. However, to date, the only legal form of incentive is a maximum of $300 to cover the cost of travel and up to 30 days of paid medical leave following the operation. One of the most successful attempts to address the supply-demand mismatch came in 1993, when a UNOS committee convened to discuss the ethical implications of “presumed consent” in which deceased individuals are presumed to have consented to cadaveric donation if they have not explicitly registered refusal to be a donor. The committee reached a verdict that this would not be an ethical practice, though this debate may be worth revisiting in light of the recent advances in organ matching systems and the potential of NEAD chains.

These are just a few examples of the ethical issues surrounding solid organ transplantation. There is still extensive debate surrounding the donation of organs from minors and children, from domesticated animals and between two HIV-positive individuals. Several less conservative ethicists have even recommended harvesting organs from executed prisoners. Other countries, like Israel, give a patient priority status on the transplant list if they are a registered organ donor. In countries like Iran, where it is legal to buy and sell organs for profit, the going price of a kidney is between $2,000 and $4,000. Organs are sold through a number of extrajudicial black markets around the globe, where kidneys are valued at an estimated $160,000.

To learn more about the world of market design and matchmaking systems, check out Alvin Roth’s book – Who Gets What – and Why: The New Economics of Matchmaking and Market Design.

Nitin Venugopal Nitin Venugopal (2 Posts)


Medical College of Georgia

Nitin Venugopal is part of the class of 2020 at the Medical College of Georgia in Augusta, GA. He is from Atlanta and graduated from Georgia Tech in 2016 with a BS in Industrial Engineering. His interests include population health and health policy.