Showing posts with label kidney exchange. Show all posts
Showing posts with label kidney exchange. Show all posts

Tuesday, March 12, 2024

Kidney exchange between Portugal and Spain, and prospects for global kidney exchange

 Here's an article from a Portuguese hospital that has engaged in kidney exchanges with Spanish hospitals that have resulted in three transplants for Portuguese patients since the program was initiated in 2017.  The paper considers how international kidney exchange can be expanded globally, so as to have significant effects on the health of Portuguese and other patients.  

The concluding  two paragraphs of the paper speak about global kidney exchange, and the controversy that it has aroused, particularly in Spain, where there has been opposition to significant cross-border kidney exchange.

Francisco, José Teixeira, Renata Carvalho, Joana Freitas, Miguel Trigo Coimbra, Sara Vilela, Manuela Almeida, Sandra Tafulo et al. "International Crossed Renal Donation – The Experience of a Single Center," Brazilian Journal of Transplantation, v. 26 (2023)

"Introduction: Kidney transplantation is the preferred treatment for end-stage chronic kidney disease, however, the shortage of organs can result in long waiting times. Living donor kidney transplantation offers an alternative to cadaver donor, but HLA or AB0 incompatibility can represent a significant obstacle. This study aimed to show the results achieved by a Portuguese hospital since its integration into an international cross-donation program, the South Alliance for Transplants (SAT). 

"Methods: The SAT program was founded in 2017 and is made up of ten Spanish hospitals, three Italian hospitals and one Portuguese hospital. The program takes place every 4 months and only enrolls pairs who are incompatible. Organ transport is carried out in partnership with the Portuguese Air Force. 

"Results: Three different crosses were carried out in partnership with three Spanish hospitals, culminating in the transplantation of three Portuguese patients out of a total of seven patients. The first crossing was carried out in March 2020, at the beginning of the COVID-19 pandemic, with the partnership of two Portuguese hospitals and a Spanish hospital, involving 1 donor/recipient pair from each country,... The second occurred in December 2021 with 3 donor/recipient pairs (1 Portuguese in which the recipient had anti-donor antibodies and positive crossmatch with the potential donor; and 2 from two Spanish hospitals),... The third crossing also took place in December 2021 with 2 donor/recipient pairs (1 Portuguese and 1 Spanish)

...

"A Global Kidney Exchange Program (GKEP), an idea initiated by Rees et al.,16 which involves kidney paired donation between high-income and low-income and medium-income countries (LMICs). Beyond the potential benefits associated with this type of transplantation, similar to those already addressed for international programs, there are concerns about the ethical implications of  such  programs.  They  may  perpetuate  existing  inequalities  between  high  and  low-income  countries,  which  has  motivated  a  statement  from  the  Declaration  of  Istanbul  Custodian  Group.17  Some  critics  argue  that  the  practices  of  most  PRMBs  lack  transparency, leaving room for exploitation and corruption,18 or raise ethical concerns regarding the commodification of organs.19On the other hand, proponents of the idea argue that a GKEP could help address the global shortage of donor organs and provide lifesaving  opportunities  for  patients  in  need.  They  also  note  that  such  programs  could  foster  collaboration  and  information-sharing between countries and institutions, potentially leading to improvements in transplant practices worldwide.16,20 Despite the controversy surrounding the proposal, the idea of a GKEP remains an intriguing possibility for advancing kidney transplantation on a global scale.

"CONCLUSION: Our experience and that of other locations show that programs like these offer numerous benefits, such as expanding the pool of available donors, improving compatibility between donors and recipients, and avoiding the costs and risks associated with desensitization therapies for ABO or HLA incompatible transplantations. These programs represent a valuable option for individuals who require a kidney transplant and can be an effective means of increasing transplant success rates and improving quality of life for patients. However, the success of these programs depends on the number of pairs enrolled. To ensure the success of these programs, there is a need for greater awareness, education, and promotion of their benefits and outcomes among the public, healthcare providers, and policymakers alike.

Tuesday, February 27, 2024

Stanford Impact Labs announces support for kidney exchange in Brazil, India, and the U.S.

 Stanford Impact Labs has announced an investment designed to help the Alliance for Paired Kidney Donation (APKD) increase access to kidney exchange in Brazil, India, and the U.S.  Here are three related web pages...

1. Stanford Impact Labs Invests in Global Collaboration to Increase Access to Kidney Transplants.  $1.5 million over three years will support solutions-focused project led by Stanford’s Dr. Alvin Roth and the Alliance for Paired Kidney Donation (APKD)  by Kate Green Tripp

"Stanford Impact Labs (SIL) is delighted to announce a $1.5 million Stage 3: Amplify Impact investment to support Extending Kidney Exchange, a solutions-focused project established to increase access to lifesaving kidney transplants.

"The team, led by Stanford’s Dr. Alvin (Al) Roth, who shared the 2012 Nobel Prize in Economics for his work on market design, and the Alliance for Paired Kidney Donation (APKD) is working in close partnership with organ transplant specialists and medical centers in Brazil, India, and the U.S., including Santa Casa de Misericórdia de Juiz de Fora, the Institute of Kidney Diseases and Research Center and Dr. H L Trivedi Institute of Transplantation Sciences (IKDRC-ITS), and Walter Reed National Military Medical Center.

"Over the course of the next three years, the team aims to increase the number of transplant opportunities available to patients who need them by creating and growing kidney exchange programs in Brazil and India, where millions of people suffer from kidney disease yet exchange is minimal; and explore the effects of initiating donor chains with a deceased donor kidney (DDIC) in the U.S., an approach which could unlock hundreds more transplants each year.

..."

2. How Does Applied Economics Maximize Kidney Transplants? A project aimed at expanding kidney exchange and saving lives puts Nobel Prize-winning matching theory into practice.  by Jenn Brown   (including a video...)

"APKD uses open source software developed by Itai Ashlagi, Professor of Management Science and Engineering at Stanford University, to facilitate the matching process for its NEAD chains, and they currently average 5 non-simultaneous transplants per chain.

3. Extending Kidney Exchange

"In Brazil, our team has launched a kidney exchange program within Santa Casa de Misericórdia de Juiz de Fora and Hospital Clínicas FMUSP in São Paulo and aims to expand to facilitating exchanges between these centers and others with the ultimate goal of kidney exchange transitioning from a research project to an officially approved practice in Brazil.

"In India, our team has deployed kidney matching software and resources for growth to the Institute of Kidney Diseases and Research Center and Dr. HL Trivedi Institute of Transplantation Sciences (IKDRC-ITS) to support kidney exchange programs. We aim to develop an evidence base for potential updates to organ transplantation laws that expand criteria for who can give and receive lifesaving kidneys.

"In the U.S., we are working with Walter Reed National Military Medical Center to test the use of deceased donor-initiated chains (DDIC) so as to generate hundreds of additional life-saving transplants each year that are not currently supported by today's practice of utilizing a deceased donor kidney to save the life of a single person on a transplant waitlist. "


 

Wednesday, February 21, 2024

Nondirected living kidney donors--Abundant (the movie, in progress)

 Abundant is a movie in the making,  a documentary about altruism, focused on non-directed living kidney donors, who start kidney exchange chains. It isn't done yet, but now they are in the editing process...

"Abundant is a feature-length documentary film about the complex, human experience of giving.  To fully understand giving, Abundant enters the world of extreme altruism.  And there are no more extreme altruists than non-directed living kidney donors.  These rare individuals give a kidney away to a complete stranger.  It’s all risk, no reward.  Or is it? 

"Abundant features true stories of non-directed kidney donors recorded live on stage at the performance art show CrowdSource for Life.  Their stories illustrate the unimaginable impact of extreme giving.  It’s obvious their kidney donations saved another person’s life, but there is so much more involved.

"Insights from experts from the worlds of economics, spirituality, business, the arts, psychology and neuroscience, frame and explain the altruistic psyche. In his interview for Abundant, Buddhist monk Bhante Sujatha described giving with a literal translation from his Sri Lankan language, Sinhala.  In Sinhala, giving means, “It leaves my hand.”  That’s a clear, simple and elegant concept.  Yet so many of us struggle with the genuine act of giving and the abundance required to give openheartedly.

"Through stories, commentary and experiences, Abundant explores how our culture struggles with abundance and what we can do to become more altruistic as a community."

#####

Update: here's a link to join the email list for updates on the movie:  https://abundantmovie.com/

Monday, February 19, 2024

Kidney exchange in the U.S. from 2006-2021

 Here's an interesting look at the (ongoing) development of kidney exchange in the U.S

Temporal trends in kidney paired donation in the United States: 2006-2021 UNOS/OPTN database analysis, by Neetika Garg, Carrie Thiessen, Peter P. Reese, Matthew Cooper, Ruthanne Leishman, John Friedewald, Asif A. Sharfuddin, Angie G. Nishio Lucar, Darshana M. Dadhania, Vineeta Kumar, Amy D. Waterman, and Didier A. Mandelbrot, American Journal of Transplantation,  24, 1, P46-56, JANUARY 2024.

Abstract: Kidney paired donation (KPD) is a major innovation that is changing the landscape of kidney transplantation in the United States. We used the 2006-2021 United Network for Organ Sharing data to examine trends over time. KPD is increasing, with 1 in 5 living donor kidney transplants (LDKTs) in 2021 facilitated by KPD. The proportion of LDKT performed via KPD was comparable for non-Whites and Whites. An increasing proportion of KPD transplants are going to non-Whites. End-chain recipients are not identified in the database. To what extent these trends reflect how end-chain kidneys are allocated, as opposed to increase in living donation among minorities, remains unclear. Half the LDKT in 2021 in sensitized (panel reactive antibody ≥ 80%) and highly sensitized (panel reactive antibody ≥ 98%) groups occurred via KPD. Yet, the proportion of KPD transplants performed in sensitized recipients has declined since 2013, likely due to changes in the deceased donor allocation policies and newer KPD strategies such as compatible KPD. In 2021, 40% of the programs reported not performing any KPD transplants. Our study highlights the need for understanding barriers to pursuing and expanding KPD at the center level and the need for more detailed and accurate data collection at the national level.

"Kidney paired donation (KPD) is rapidly evolving and reshaping the landscape of living donor kidney transplantation (LDKT). Since the initial KPD transplants performed in the United States in 1999,1 the scope of KPD has expanded substantially. With the inclusion of nondirected donor,2 it has progressed from simple 2-way or multiple-way exchanges to nonsimultaneous kidney donor chains3 and, more recently, to advanced and voucher donations.4 Downstream from nondirected donors, chains often conclude with end-chain kidneys allocated to candidates on the deceased kidney donor waitlist without a living donor (LD).5 Historically used to overcome the barrier of ABO/human leukocyte antigens (HLA) incompatibility, KPD is being increasingly used by compatible donor-recipient pairs to obtain more suitable kidneys for the respective recipients.6 KPD programs can be single center or internal, regional, or national.7,8 The largest multicenter or national KPD programs in the United States are the National Kidney Registry,9 the Alliance for Paired Donation,10 the MatchGrid/Medsleuth program,11 and the program operated by the Organ Procurement and Transplantation Network (OPTN).12 While multicenter KPD often expands the pool of candidates to improve match possibilities, there are examples of very successful single-center programs."

Tuesday, February 6, 2024

Kidney exchange (and other bits of market design) in the New York Times

 Peter Coy, the veteran New York Times economics columnist, writes about kidney exchange, after an interview/conversation sparked by a recent working paper of mine, Market Design and Maintenance. (He's a rare economic journalist who reads economists' papers.)

Here's his column, published yesterday afternoon:

The Economist Who Helped Patients Get New Kidneys, Feb. 5, 2024, 3:00 p.m. ET, By Peter Coy

He's also a rare interviewer: his column includes the names of more of my coauthors than I can recall in any other interview. In order of appearance: Tayfun Sonmez and Utku Unver, Frank Delmonico, Susan Saidman, Mike Rees (implicitly) when he names Mike's nonprofit Alliance for Paired Kidney Donation, and Elliott Peranson.  Market design is, after all, a team sport.

Here's his concluding paragraph:

"What is it like to straddle the worlds of academia and practice? I asked. “It takes a lot of patience,” he said. “Market design is outward-facing. I learn from trying to persuade people who aren’t economists. It’s a lot of fun also. Sometimes you have to go beyond your completely reliable scientific knowledge.”

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Earlier post:

Monday, December 11, 2023

Tuesday, December 26, 2023

Market Design in El Mercurio--Chile's oldest newspaper

Last Tuesday, in Chile I was interviewed by Eduardo Olivares, the editor for Economics and Business of El Mercurio,  which published the interview yesterday. We talked for an hour about market design generally, about how markets work when they're working well or working badly, and we spoke about school choice (where Chile is a leader) and transplantation (where it is not). The interview is behind a paywall, but below are some extracts (retranslated back into English via Google Translate).

On markets generally:

—Many people ask that “markets be free,” as has recently happened in Argentina. Should they be free?

“That's a complicated question. Markets should be free to function well, but they need conditions that allow them to function well. Having a free market does not necessarily mean a market without rules. A wheel can spin freely because it has a well-greased axle and bearings. A wheel by itself cannot turn very well, and the same goes for the market.”

—Who puts the oil in the wheel gears?

“That's the job of market design. Part of what makes markets work well are good market rules. The government has a role in regulating markets, concerning property rights and things like that. But on another level, entrepreneurs do things. Here in Santiago I [can]... call an Uber using the same app and rules I use in California. Uber is a marketplace for passengers and drivers. The rules can be made by both private organizations and the government.”

On prices:

—Do prices matter?

"A lot. “Prices are important to help allocate scarce resources, but also to make them less scarce.”

...

—When do they not matter?

“Let me start with when they matter a lot: in commodity markets. If you want to buy commodities, price is really the only thing that's happening. But when 'El Mercurio' wants to hire journalists, it doesn't limit itself to offering a salary: it wants it to be a good job, with special reporters. Price is important, but in other markets other things are also important. When you get a new job, the first question your friends ask you is not what the salary is, but who you work for.”

On school choice:

“Most markets are not commodity markets... In some markets we don't like prices to work at all. One of the places where Chile is a leader in market design is school choice: how people are assigned to schools and Chile has done a lot of work on this, although mainly for public schools.”

—What do you know about this system in Chile?

“Not long ago, before there was centralized and widespread school choice in Chile, there were the usual problems with decentralized school choice; That is, parents had to get up early to get in line, and they had a difficult process to register their children.”

—The new system has been criticized. Some claim it caused more people to choose the private system over the public school system. Isn't it similar to what is happening in New York, for example?

“There is something to that. In New York and Boston we also have a system that we call charter schools: free access schools, but organized by private entities, even if they are municipal schools. And they also have different standards. School choice is important, but it does not solve the problems of poverty or income inequality. Now, one of the reasons we have school choice in the United States and perhaps also in Chile is because we think that, otherwise, there is a danger that the poor will be condemned to send their children to poor schools. .

—Has there been any successful case in which parents can honestly rank the order of preference for the school they want their children to go to?

“In Chile, procedures are used that [make it] what game  theorists call a dominant strategy to express true preferences. The [remaining] problem is not in creating systems that make it safe to express preferences, but in distributing the information so that people can form preferences sensibly. In the United States, the hardest families to reach are those who don't speak English at home, so it's sometimes difficult to communicate with them. And different families have different feelings about what kind of schools their children should attend.”

“The benefits of school choice come from the fact that some schools may be high quality for some children but not for others, so we would like children to attend the schools that are best quality for them.”

On kidneys:

—You are famous for the proposal that allowed the “kidney exchange.” Years after the first experience, what do you see now in this type of market?

“Kidney exchange is working quite well in the US, but it works especially well for patients who are not too difficult to match. Even in the US, a fairly large country, we have patients who are so difficult to match that we have trouble finding a kidney for them.”

—And in other countries?

“Smaller countries, with 20 million inhabitants, like Chile, would benefit if we could make national borders not so important. When we look at transplants per million inhabitants, Chile is in the middle of the world. But since it is a small country, when the total number of transplants performed is analyzed, Chile has very few. Kidneys are obtained from both deceased and living donors. In Chile, as in much of the world, the majority of transplants come from deceased donors. Kidney exchange would allow more transplants to come from living donors ... “Twenty million is not enough, so it would be very good to see in South America an exchange of kidneys that can cross between countries, which is not so easy to do.”

Equality of exchange and the role of perceptions

“One of the things that worries people when talking about transplants is that [they think it might be] a medical process that exploits the poor. Of course, the thing about kidney exchange is that each pair of people gives one kidney and receives one kidney. It is very egalitarian. I think kidney exchange is a good place to combat this notion that transplantation is like trafficking,” he notes.

—Notions, perceptions are very important. Many people think of “exchange” as the exchange of securities in the stock market.

“That's right, but not every exchange involves money. One of the discussions about money in the world that is taking place in the European Union at the moment is about payment to blood plasma donors. In the EU, only Germany, Austria, the Czech Republic and Hungary pay blood plasma donors. And those are the only EU countries that have as much blood plasma as they need. The others have to import everything, and they do it from the United States. The United States is the Saudi Arabia of blood plasma (…) The World Health Organization says that plasma must be obtained in each country, and from unpaid donors. You have to be self-sufficient... an economist finds that a little funny. Blood is a matter of life and death. “When there is a pandemic, we do not tell countries that they must be self-sufficient [in vaccines].”

—When we talk about these exchanges of blood plasma and kidneys, school choice systems, we are talking about the same idea: coincident or paired markets. But the concept of the market has been so questioned, especially by some political groups, for so long...

"It's true. Now,  kidney exchange is special because money doesn't change hands. Money changes hands to get medical care, you have to pay doctors, nurses and hospitals. But we are not talking about buying kidneys from donors, but rather that, at the patient level, each pair receives a kidney and donates a kidney. It is radically egalitarian. Many people who think about markets may not think of it as a market, but I think that's a mistake. Many markets are not just about money… we would worry much less about markets if income and wealth inequality did not exist. “What worries us about markets is that some people are poor and some people are rich, and markets seem like a way to give the rich an advantage.”

“There is no doubt that being rich is better than being poor. The real question is what do we do to alleviate poverty. Making it invisible is not the same as alleviating it. One of the reasons I think many countries don't allow blood and plasma donors to be paid is because they don't like the way that looks. It reminds them that some people would like to get some money and would donate blood for it.”







Apparently, according to the caption, I'm "affable and smiling" (although not in this picture:)

I was in Chile to participate in what turned out to be a wonderful workshop on market design at the University of Chile, organized by Itai Ashlagi, José Correa, and Juan Escobar.
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Update (Dec. 27): Here's an account of my closing public talk from the U. Chile's Center for Mathematical Modeling, one of the hosts of the market design workshop.

And here's a picture at the close, including some of those mentioned above: At my far left in the picture is José Correa,  who in addition to his other roles is Vice Rector for Information Technologies. Next to him is Alejandra Mizala, prorrector (provost) of the university.  Next to her (immediately to my left) is Rector of the University of Chile, Rosa Devés, and immediately to my right is market designer and director of the MIPP Millennium Institute, Juan Escobar. Next to him is Héctor Ramírez, director of the Center for Mathematical Modeling. And next to him (at my far right) is professor Rafael Epstein who (along with Correa, Escobar, and his daughter Natalie Epstein) has been involved with school choice in Chile, among other things.



Sunday, December 24, 2023

Kidney exchange as an innovation in organization

Here's a two minute video summary of an address I gave in 2014, just noticed now, which seems still pretty up to date. A lot of progress has been made through new ways of organizing  transplants, and there's plenty of organizational innovation still needed.

State-of-the-Art Address - World Transplant Congress 2014
   
 

Saturday, December 2, 2023

Design of (international) kidney exchange: ex-post rejection versus ex-ante withholding

 Here's a paper by several Dutch computer scientists, which seems to be motivated by the problem of international kidney exchange within the EU, in which there are lots of concerns about fairness between countries.  But (as the paper notes) these could also apply to individual transplant centers, in the U.S. context.  The thrust of the paper is that looking for exchanges that won't be rejected ex post in a full information environment may be more productive than looking for ways to incentivize countries or transplant centers to reveal their full sets of patient donor pairs in an incomplete information environment.

Blom, Danny, Bart Smeulders, and Frits Spieksma. "Rejection-Proof Mechanisms for Multi-Agent Kidney Exchange." Games and Economic Behavior (2023).

Abstract: Kidney exchange programs (KEPs) increase kidney transplantation by facilitating the exchange of incompatible donors. Increasing the scale of KEPs leads to more opportunities for transplants. Collaboration between transplant organizations (agents) is thus desirable. As agents are primarily interested in providing transplants for their own patients, collaboration requires balancing individual and common objectives. In this paper, we consider ex-post strategic behavior, where agents can modify a proposed set of kidney exchanges. We introduce the class of rejection-proof mechanisms, which propose a set of exchanges such that agents have no incentive to reject them. We provide an exact mechanism and establish that the underlying optimization problem is 


we also describe computationally less demanding heuristic mechanisms. We show rejection-proofness can be achieved at a limited cost for typical instances. Furthermore, our experiments show that the proposed rejection-proof mechanisms also remove incentives for strategic behavior in the ex-ante setting, where agents withhold information.

Monday, November 20, 2023

Global kidney exchange between Denmark and U.S.

 Here's a news story from North Carolina, home of one of the patient-donor pairs in the U.S.-Denmark kidney exchange, organized by the Alliance for Paired Kidney Donation (APKD).

Worldwide kidney transplant chain saves lives in Raleigh, Denmark, Colorado. by: Maggie Newland

"RALEIGH, N.C. (WNCN) — When a Raleigh musician needed a kidney, a friend of a friend offered to donate hers. The offer led to a kidney transplant chain stretching from the Triangle all the way to Denmark.

...

"Meanwhile, across the ocean, in Denmark, friends Peter Wichmann and Morton Berktoft were dealing with a similar issue. Wichmann wanted to donate his kidney to Berktoft, but they didn’t match either.

"Then something called a paired kidney exchange ended up helping all of them.  

"“It’s actually a Nobel prize-winning algorithm,” explained Krista Sweeney with AKPD. “They put these pairs into our system… We’re able to identify the best matches for each pair.”

"In this case, Kovacic donated her kidney to someone in Colorado. Their loved one donated a kidney to Berktoft, who flew to the U.S. for the surgery along with Wichmann, who donated a kidney to Adamo.

...

"Three months after the surgeries the donors and recipients are all doing well and got a chance to talk to each other in a virtual meeting.

...

“Even though the paired exchange wasn’t our initial plan it worked out so great for six people,” said Kovacic. “And three people’s lives to be saved.”

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Earlier posts on Denmark-US exchange:

Monday, June 7, 2021

Friday, November 17, 2023

Report From a Multidisciplinary Symposium on the Future of Living Kidney Donor Transplantation

 How might we increase the number of lifesaving transplants from living kidney donors? Might we one day be able to reward donors? And what might we do until then, while we wait for something that will eventually replace human organ transplantation?  Here's the published account of last year's symposium.

Thomas G. Peters, John J. Fung, Janet Radcliffe-Richards, Sally Satel, Alvin E. Roth, Frank McCormick, Martha Gershun, Arthur J. Matas, John P. Roberts, Josh Morrison, Glenn M. Chertow, Laurie D. Lee, Philip J. Held, and Akinlolu Ojo, “Report From a Multidisciplinary Symposium on the Future of Living Kidney Donor Transplantation,” Progress in Transplantation  (forthcoming), Online first, Nov 15, 2023 https://journals.sagepub.com/doi/full/10.1177/15269248231212911  (pdf here).

Abstract: Virtually all clinicians agree that living donor renal transplantation is the optimal treatment for permanent loss of kidney function. Yet, living donor kidney transplantation has not grown in the United States for more than 2 decades. A virtual symposium gathered experts to examine this shortcoming and to stimulate and clarify issues salient to improving living donation. The ethical principles of rewarding kidney donors and the limits of altruism as the exclusive compelling stimulus for donation were emphasized. Concepts that donor incentives could save up to 40 000 lives annually and considerable taxpayer dollars were examined, and survey data confirmed voter support for donor compensation. Objections to rewarding donors were also presented. Living donor kidney exchanges and limited numbers of deceased donor kidneys were reviewed. Discussants found consensus that attempts to increase living donation should include removing artificial barriers in donor evaluation, expansion of living donor chains, affirming the safety of live kidney donation, and assurance that donors incur no expense. If the current legal and practice standards persist, living kidney donation will fail to achieve its true potential to save lives.

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Links to videos of the symposium presentations are here:

Thursday, November 16, 2023

Top trading cycles 'respect improvements' by rewarding agents whose endowments become more desirable

 Here's a wide-ranging paper that explores the way the Top Tradinig Cycles (TTC) algorithm 'respects improvements' by rewarding an agent whose endowment becomes more desirable.

Biró, Péter, Flip Klijn, Xenia Klimentova, and Ana Viana. "Shapley–Scarf Housing Markets: Respecting Improvement, Integer Programming, and Kidney Exchange." Mathematics of Operations Research (2023).

"Abstract: In a housing market of Shapley and Scarf, each agent is endowed with one indivisible object and has preferences over all objects. An allocation of the objects is in the (strong) core if there exists no (weakly) blocking coalition. We show that, for strict preferences, the unique strong core allocation “respects improvement”—if an agent’s object becomes more desirable for some other agents, then the agent’s allotment in the unique strong core allocation weakly improves. We extend this result to weak preferences for both the strong core (conditional on nonemptiness) and the set of competitive allocations (using probabilistic allocations and stochastic dominance). There are no counterparts of the latter two results in the two-sided matching literature. We provide examples to show how our results break down when there is a bound on the length of exchange cycles. Respecting improvements is an important property for applications of the housing markets model, such as kidney exchange: it incentivizes each patient to bring the best possible set of donors to the market. We conduct computer simulations using markets that resemble the pools of kidney exchange programs. We compare the game-theoretical solutions with current techniques (maximum size and maximum weight allocations) in terms of violations of the respecting improvement property. We find that game-theoretical solutions fare much better at respecting improvements even when exchange cycles are bounded, and they do so at a low efficiency cost. As a stepping stone for our simulations, we provide novel integer programming formulations for computing core, competitive, and strong core allocations."

Here is their literature review:

"The nonemptiness of the core is proved in Shapley and Scarf [47] by showing the balancedness of the corresponding nontransferable utility game and also in a constructive way by showing that David Gale’s famous top trading cycles (TTC) algorithm always yields competitive allocations. Roth and Postlewaite [40] later show that, for strict preferences, the TTC results in the unique strong core allocation, which coincides with the unique competitive allocation in this case. However, if preferences are not strict (i.e., ties are present), the strong core can be empty or contain more than one allocation, but the TTC still produces all competitive allocations. Wako [50] shows that the strong core is always a subset of the set of competitive allocations. Quint and Wako [39] provide an efficient algorithm for finding a strong core allocation whenever there exists one. Their work is further generalized and simplified by Cechlárová and Fleiner [19], who use graph models. Wako [52] shows that the set of competitive allocations coincides with the core based on an antisymmetric weak domination concept, which we refer to as Wako-core in this paper. This equivalence is key for our extension of the definition of competitive allocations to the case of bounded exchange cycles.

1.2.2. Respecting Improvement.

"For Gale and Shapley’s [23] college admissions model, Balinski and Sönmez [11] prove that SOSM respects improvement of student’s quality. Kominers [29] generalizes this result to more general settings. Balinski and Sönmez [11] also show that SOSM is the unique stable mechanism that respects improvement of student quality. Abdulkadiroğlu and Sönmez [3] propose and discuss the use of TTC in a model of school choice, which is closely related to the college admissions model. Abdulkadiroğlu and Che [2] state and Hatfield et al. [25] formally prove that the TTC mechanism respects improvement of student quality.

"Hatfield et al. [25] also focus on the other side of the market and study the existence of mechanisms that respect improvement of a college’s quality. The fact that colleges can match with multiple students leads to a strong impossibility result: they prove that there is no stable or Pareto-efficient mechanism that respects improvement of a college’s quality. In particular, the (Pareto-efficient) TTC mechanism does not respect improvement of a college’s quality.

"In the context of KEPs with pairwise exchanges, the incentives for bringing an additional donor to the exchange pool was first studied by Roth et al. [42]. In the model of housing markets their donor-monotonicity property boils down to the respecting improvement property. They show that so-called priority mechanisms are donor-monotonic if each agent’s preferences are dichotomous, that is, the agent is indifferent between all acceptable donors. However, if agents have nondichotomous preferences, then any mechanism that maximizes the number of pairwise exchanges (so, in particular, any priority mechanism) does not respect improvement. This can be easily seen by means of Example 4 in Section 3.3.

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See also

The core of housing markets from an agent’s perspective: Is it worth sprucing up your home?  by Ildiko Schlotter, , Peter Biro, and Tamas Fleiner

Abstract. We study housing markets as introduced by Shapley and Scarf (1974). We investigate the computational complexity of various questions regarding the situation of an agent a in a housing market Hwe show that it is NP-hard to find an allocation in the core of H where (i) a receives a certain house, (ii) a does not receive a certain house, or (iii) a receives a house other than her own. We prove that the core of housing markets respects improvement in the following sense: given an allocation in the core of H where agent a receives a house h, if the value of the house owned by a increases, then the resulting housing market admits an allocation in its core in which a receives either h or a house that a prefers to h; moreover, such an allocation can be found efficiently. We further show an analogous result in the Stable Roommates setting by proving that stable matchings in a one-sided market also respect improvement.


Friday, November 10, 2023

Kidney Exchange: Within and Across Borders (video lecture).

 Below is a video of my 40 minute talk at Berkeley on Monday, on Kidney Exchange: Within and Across Borders, at the final workshop on Mathematics and Computer Science of Market and Mechanism Design,  at the Simons Laufer Mathematical Sciences Institute (SLMath). (But we warned or reassured, this isn't a mathematical lecture...)


Here's another link to the video if you have trouble connecting:  https://www.slmath.org/workshops/1082/schedules/34227

Tuesday, October 3, 2023

Transplant grand rounds in Manitoba, tomorrow on kidney exchange

 I'll be talking tomorrow to the transplant pros in Manitoba, about kidney exchange and transplants across borders, among other things.

Wednesday, Oct 4, 2023 | 1:15 PM CST



Thursday, September 28, 2023

The growing role of kidney exchange in the U.S.

 Here's a paper accepted for publication in the American Journal of Transplantation, tracing the growing role of kidney exchange in the U.S. (But much remains to be done...)

Temporal Trends in Kidney Paired Donation in the United States: 2006 – 2021 UNOS/OPTN Database Analysis  by Neetika Garg, MD, Carrie Thiessen, MD, PhD, Peter P. Reese, MD, PhD, Matthew Cooper, MD, Ruthanne Leishman, RN, MPH, John Friedewald, MD, Asif A. Sharfuddin, MD, Angie G. Nishio Lucar, MD, Darshana M. Dadhania, MD, MS, Vineeta Kumar, MD, Amy D. Waterman, PhD, Didier A. Mandelbrot, MD  PII: S1600-6135(23)00694-9 DOI: https://doi.org/10.1016/j.ajt.2023.09.006 To appear in: American Journal of Transplantation

Abstract:  Kidney paired donation (KPD) is a major innovation that is changing the landscape of kidney transplantation in the United States. We used the 2006 - 2021 United Network for Organ Sharing data to examine trends over time. KPD is increasing, with one in 5 living donor kidney transplants (LDKT) in 2021 facilitated by KPD. The proportion of LDKT performed via KPD was comparable for non-Whites and Whites. An increasing proportion of KPD transplants is going to non-Whites. End-chain recipients are not identified in the database. To what extent these trends reflect how end-chain kidneys are allocated, as opposed to increase in living donation among minorities, remains unclear. Half the LDKT in 2021 in sensitized (PRA ≥80%) and highly sensitized (PRA ≥98%) groups occurred via KPD. Yet, the proportion of KPD transplants performed in sensitized recipients has declined since 2013, likely due to changes in the deceased donor allocation policies and newer KPD strategies such as compatible KPD. In 2021, 40% of the programs reported not performing any KPD transplants. Our study highlights the need for understanding barriers to pursuing and expanding KPD at the center level, and the need for more detailed and accurate data collection at the national level.


Monday, September 18, 2023

Kidney Paired Donation in Developing Countries: a Global Perspective

 Vivek Kute and his colleagues argue that one of the lessons from the developing world is that kidney exchange can save many lives, but may need to be organized differently in some ways than in the developed world.

Kidney Paired Donation in Developing Countries: a Global Perspective by Vivek B. Kute, Vidya A. Fleetwood, Sanshriti Chauhan, Hari Shankar Meshram, Yasar Caliskan, Chintalapati Varma, Halil Yazıcı, Özgür Akın Oto & Krista L. Lentine, Current Transplantation Reports (2023)  (here's a link that may provide better access]


Abstract

...

"Despite the advantages of KPD programs, they remain rare among developing nations, and the programs that exist have many differences with those of in developed countries. There is a paucity of literature and lack of published data on KPD from most of the developing nations. Expanding KPD programs may require the adoption of features and innovations of successful KPD programs. Cooperation with national and international societies should be encouraged to ensure endorsement and sharing of best practices.

Summary

KPD is in the initial stages or has not yet started in the majority of the emerging nations. But the logistics and strategies required to implement KPD in developing nations differ from other parts of the world. By learning from the KPD experience in developing countries and adapting to their unique needs, it should be possible to expand access to KPD to allow more transplants to happen for patients in need worldwide."

...

" Despite the advantages of KPD programs, they remain rare in the developing world, and the programs that exist have many differences with those of developed countries. Program structure is one of these differences: multi-center, regional, and national KPD programs (Swiss, Australia, Canada, Dutch, UK, USA) are more common in the developed than the developing world, whereas single center programs are more common

...

"kidney exchanges frequently take weeks to months to obtain legal permission in India despite the fact that only closely-related family members (i.e., parents, spouse, siblings, children, and grandparents) are allowed to donate a kidney [47].

...

"Protecting the privacy of a donor, including maintaining anonymity when requested, is common practice among developed countries but uncommon in developing nations. Anonymous allocation during KPD is a standard practice in the Netherlands, Sweden, and other parts of Europe, but this is not the case in countries such as India, Korea, and Romania [14, 48, 49]. In areas where anonymity is not maintained, the intended donor/recipient pair must meet and share medical information once a potential exchange is identified, but before formal allocation of pairs occurs. The original donor/ recipient pair may refuse the proposed exchange option for any reason and continue to be on the waitlist. In India, nonanonymous KPD allocation is standard practice and has the goal of increasing trust and transparency between the transplant team and the administrative team [14, 49]. Countries differ in philosophical approaches to optimizing trust and transparency, and objective data on most effective practices would benefit the global community."

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Tomorrow I hope to have a few words to say about the equally unique situation in China.

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Update:

Tuesday, September 19, 2023

Sunday, August 27, 2023

THE 18TH CONGRESS OF ASIAN SOCIETY OF TRANSPLANTATION (CAST) 25 -28 August 2023 • Hong Kong

Tonight, Sunday, at 5:30pm California time, I'll be opening the Monday morning session in Hong Kong of the THE 18TH CONGRESS OF ASIAN SOCIETY OF TRANSPLANTATION 25 -28 August 2023.

Keynote Lecture
28 Aug 0815-0915 Theatre 1 Keynote Lecture III
Chairs : Albert CY CHAN, Hong Kong, China
Hai-Bo WANG, Mainland China
Topic 1. Transplant economics Alvin ROTH USA
Topic 2. Organ transplantation reform in China: The synergy of Chinese cultural traditions and WHO guiding principle  Jie-Fu HUANG Mainland China


Friday, August 18, 2023

Kidney exchange between Portugal and Italy

 Italy-Portugal cross transplants. that click that saved two

"Thanks to a complex work of intervention planning and logistics, managed by the National Transplant Center, the Veneto Regional Transplant Center and the Portuguese institutions, the kidney of the Italian donor was removed in Vicenza and transplanted in Porto in a 41-year-old man while the Italian patient was transplanted with a kidney donated by a 36-year-old woman. The organs were harvested in the two centers simultaneously on the morning of 20 July. The Portuguese kidney arrived at Treviso airport at 2.10 pm on board a Lusitanian Air Force flight: the military delivered the organ to the regional transplant coordinator of the Veneto, Dr. Giuseppe Feltrin, receiving the Italian kidney in exchange. The 118 of Vicenza immediately transported the organ to San Bortolo where the transplantation began immediately. Both surgeries were successful and all recipients and donors went home in excellent condition."

Thursday, July 27, 2023

Kidney brouhaha in Israel: is a good deed still good when performed by a shmuck?

 Recently a three way kidney exchange was performed in Israel. This would have been unremarkable under most circumstances: Israel has an active kidney exchange system.  But it caused a strong reaction in the Israeli press, because one of the donors, a  well-known rightwing activist who wanted to donate a kidney so that his brother could receive one, announced that he wanted his kidney to go only to a Jew.

Here's the Ynet story (you can click to render it in English):

 kidney in a transplant marathon: "The condition was - only for a Jew

Here's the Times of Israel (already in English):

Right-wing journalist causes stir by announcing his kidney would go only to a Jew

There were many more, but you get the idea.  Some of the stories point out that the Israeli National Transplantation Center uses an algorithm* that doesn't see the religion of the recipient, so it's not clear that this was a declaration with consequences.  It was meant to provoke, and it did.

But it's a complicated issue.  In the U.S. (and in Israel), donations can be made to a specific individual, but not to a class of individuals.  With living donation, it means that the donor can choose a specific person to donate to, and it isn't an issue how they choose: no one has to donate an organ to anyone, and every donation saves a life (and maybe more than one, particularly since  living donation reduces competition for scarce deceased-donor kidneys). So if this donor had been able to donate to his brother, no one would have thought twice that he was glad to be donating to a fellow Jew.  What made his announcement provocative was that his kidney wasn't going to his brother: his brother was getting a kidney from an anonymous other donor. [Update clarification/correction: this donation was apparently an undirected (except for the 'only' condition) altruistic donation, not part of an exchange involving the donor's brother.]

Among the people I corresponded with about this is Martha Gershun, a kidney donor who thinks and writes clearly, and has given me permission to quote some of what she said.

"I’m wondering if we find the presentation of the story troubling:  “Right-wing journalist and Temple Mount activist causes stir by announcing his kidney would go only to a Jew.”  We would react badly to a story that said:  “Right-wing Trump supporter says he will only give his kidney to a white man.”

"What if instead the stories were:  “Observant Jewish father of 8 wants to donate to a fellow Jew” and “Rural man from West Virginia seeks to help another in his community”?  Would we find those stories more acceptable?"

Part of the feeling that this is a bit complicated has to do with the fact that we don't (and maybe shouldn't) look gift horses in the mouth, i.e. we don't and maybe shouldn't delve deeply into the motivation of altruistic acts that do a lot of good. We should applaud good deeds even if they aren't performed by saints. (I blogged yesterday, about paying it forward, an umbrella term for doing good deeds in a spirit of gratitude for having ourselves benefited  from past good deeds performed by others. We generally don't find it necessary to condition our approval on precisely who receives the forward-paid gifts.)

So, while I'm not sorry to see that this statement by a kidney donor is a much discussed provocation, I'm inclined to think that a good deed remains a mitzvah even if not performed by a tzadik, as we might have said in our New York English when I was growing up.

I'll give the last word to a Haaretz op-ed, also in English:

 Is It Kosher to Donate Kidneys Only to Other Jews?  A well-known religious journalist in Israel declared the " -only" donation of his kidney. His act is imperfect, but not immoral by Robby Berman

+++++++++++++++

*On the algorithm used in Israel and elsewhere, see e.g.

Wednesday, January 15, 2020 Kidney Exchange in Israel (supported by Itai Ashlagi)


and


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Update: related subsequent post 


Wednesday, July 26, 2023

Paying it forward

 Scott Cunningham, an economist who devotes a lot of his efforts to providing public goods, recently had a post on the phrase "paying it forward." He writes that he connected it with a movie with a similar name, but has recently come to view it differently (for reasons I find too embarrassing to quote, but related to the fact that I use the phrase now and then.)

Wikipedia says "Pay it forward is an expression for describing the beneficiary of a good deed repaying the kindness to others instead of to the original benefactor."  It goes on to say "Robert Heinlein's 1951 novel Between Planets helped popularize the phrase."  I could have first seen it there, as I read much of Heinlein's science fiction when I was a boy.

My associations with the phrase now mostly come from the motivations and actions of some living kidney donors, particularly in kidney exchange chains.

The phrase is certainly is evocative of what we do so much of in academia (when we're doing academia well): it describes the relationship between studying and teaching, and between teachers and students.

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Scott's post announced that, as part of paying things forward, he's funding a prize for young economists.



Thursday, July 13, 2023

Laurie Lee interviews me about kidney exchange, repugnance, and more (podcast)

 Laurie Lee interviews me in her podcast Donor Diaries.

https://www.buzzsprout.com/1748941/13094958?t=35 (You don’t have to log in; just click on “Listen Now”.)

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Here is her written description:

"Exchanging kidneys is a complicated process that involves multiple collaborations between kidney patients, living donors, transplant centers, insurance companies, airlines and more.  It’s truly remarkable if you stop to think about the number of people and organizations that need to come together to make 1 paired exchange possible.  We only started exchanging kidneys between non-compatible pairs a little over 20 years ago, so it’s a somewhat new process.  Have you ever wondered how this was made possible?

"Meet Nobel Laureate Al Roth who is an economist and Stanford University professor.  Al designs markets.  He’s one of the prominent players who has made kidney exchange possible.  In a nutshell, his work has revolutionized kidney exchange around the world by using economic theory to make kidneys more available.

"In October 2012, Al was the co-recipient of the 2012 Nobel Memorial Prize in Economic Sciences, together with Lloyd S. Shapley, for “ the theory of stable allocations and the practice of market design."

"Al Roth is well known for his application of economics to real world problems.  In this podcast episode we touch a wide range of topics ranging from paired exchanges, prostitution, surrogacy, and more.  All of these markets are examples of repugnant markets.  Kidney Donation can be characterized as a repugnant market, and Al will tell us all about it! 

Links: