Four international kidney exchange programs: 3 achieve substantial success

 Here's a paper reporting on the experience of four cross-border kidney exchange programs, whose experience teaches an important lesson.  In particular (see the figure below), one of  the programs is run by Spain, Italy and Portugal, whose  total population of approximately 118 million people is far larger than the combined population of the other three*, but manages to do less than 5% of the total cross-border exchanges, far fewer than any of the others.  Despite its size, the Spain-Italy-Portugal program only tries to match hard-to-match patient-donor pairs with other hard-to-match pairs, unlike the other three programs.

 International Kidney Paired Donation Programs: Evolution and Practices of 4 Large Collaborations
Klimentova, Xenia PhD1; Domínguez-Gil, Beatriz MD, PhD2; Viana, Ana PhD1,3; Manlove, David PhD4; Andersson, Tommy PhD5; Ashkenazi, Tamar RN, PhD6; Berlakovich, Gabriela MD7; Böhmig, Georg A. MD8; Burton, Jo RN, PGDip9; Coll, Elisabeth MD, PhD2; Dittmer, Ian FRACP9; Fiaschetti, Pamela MD10; Fronek, Jiri MD, PhD11; Hughes, Peter D. MBBS, PhD12,13; Ivo da Silva, Margarida MD14; Mor, Eytan MD15; Viklický, Ondřej MD, PhD16; Weinreich, Ilse Duus BMLS17; Ferrari, Paolo MD, FRACP18,19
Transplantation ():10.1097/TP.0000000000005602, December 24, 2025. | DOI: 10.1097/TP.0000000000005602

"Plain Language Summary: Kidney paired donation (KPD) programs are organized in various countries to facilitate the donation of kidneys from willing but incompatible donors by matching them with pairs in similar situations. These programs often struggle with an accumulation of difficult-to-match recipients and small pools of incompatible pairs. To address this, several international collaborations have emerged to expand the pool sizes and increase the number of transplants by “exchanging” donors’ kidneys across countries. We identified 4 established international KPD programs, each supported by protocols and agreements signed by the participating parties. Each program is presented separately, detailing its historical establishment, operational aspects, and statistics on pool characteristics and performance. Following this, we provide a comparative analysis of key aspects across the 4 programs. Each program has its unique context and specificities. Even though 3 of 4 collaborations started just before the COVID-19 pandemic, they have collectively facilitated >450 transplants. This underscores the importance of further developing these collaborations to share practices and experiences, and to facilitate more transplants, particularly for difficult-to-match recipients. Three of the 4 presented collaborations are either fully operated or led by European countries. This highlights the crucial role of ongoing international cooperation in the development of KPDs, in particular in Europe. By further promoting collaboration among countries, we can facilitate pan-European exchanges and improve access to live kidney transplants for patients in need.

 ...

"A fundamental difference between the programs is their collaboration model. STEP, ANZKX, and the Czech-Austrian-Israeli collaboration operate as “merged pool” model, where all participating pairs are combined for joint matching runs. For STEP and ANZKX, no other matching runs are conducted by partners at any level (hospital or national), whereas in the Czech-Austrian-Israeli collaboration, the Austrian and Israeli partners report performing local exchanges whenever compatible pairs are identified.
 

"In contrast, KEPSAT uses a “sequential pool” model, where national matches are attempted first, and only unmatched pairs are entered into the international pool. It is recognized that the last 2 strategy strategies may lead to a fragmented market, potentially limiting matches for highly sensitized patients, as easier-to-match pairs are removed beforehand."

 It's ironic that a program that appears to be intended primarily to help hard-to-match pairs is organized in a way that limits them in this way.

The paper concludes on an optimistic note (with which I fully agree):

"In conclusion, ongoing international cooperation is essential for advancing KPD programs globally. Expanding cross-border exchanges and improving access to kidney transplants can greatly benefit patients worldwide. Additional strategies, such as NDADs, desensitization protocols, and the inclusion of compatible pairs, can further enhance the effectiveness of both national and international programs. Oversight of these initiatives is crucial to safeguarding the welfare of both donors and recipients, as well as to maximizing the success rates of kidney transplants.
 

"Looking ahead, new initiatives, and projects, funded by international health organizations, such as the European Kidney Paired Exchange Programme project (https://www.hnbts.hu/euro-kep/project), funded by EU4Health and starting in November 2024, aim to expand global collaboration among KPD programs, building on and strengthening existing partnerships. This increased international cooperation is expected to create additional opportunities for patients in need of kidney transplants worldwide, making life-saving transplants accessible to more individuals regardless of their geographic location."

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Earlier: Portuguese transplant docs noted the problem and argued for more global kidney exchange:

Tuesday, March 12, 2024 Kidney exchange between Portugal and Spain, and prospects for global kidney exchange

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*Notes on population:

Spain: 49 million; Italy 59 million; Portugal 10 million ; KEPSAT total pop =  approx 118 million

 Australia 28 million; NZ 5 million: ANZKX total pop approx 33 million

Austria: 9 million, Czech Republic  11 million, Israel 10 million: AT-CZ-IL total 30 million

Sweden: 11 million; Norway:  6 million; Denmark 6 million; Finland  6 million: STEP total approx 29 mil

Admissions to polytechnics in Finland, by Kristian Koerselman

Here's a paper that gives a very clear description of the centralized application process for Finnish polytechnics (applied universities), which gives applicants a complicated strategic problem, and results in many applicants re-applying in subsequent years.

Assignments are by a (school proposing) deferred acceptance algorithm, but applicants get extra points in a school's preferences by listing it first, they can only list four programs, and they must choose which exams to take.

Why Finnish polytechnics reject top applicants
Kristian Koerselman
Education Economics, July 2020

"The Finnish polytechnic assignment provides us with an example where applicants are asked to strategize in their applications while having poor prior information on the set of programs that would admit them. These features should in and of themselves already be expected to cause a poor assignment outcome. I highlight the additional role which entrance exams appear to play in creating what should arguably be seen as a misrepresentation of true admission criteria analogous to a misrepresentation of applicants' true preferences. Because applicants take and retake different entrance exams in different years, programs rank the same applicants differently in different years, giving applicants an incentive to reapply even if they were originally assigned to their within-year most preferred feasible program.
...
"Finland provides 9 years of compulsory, comprehensive education, after which almost all students continue in approximately equal proportions to either an academically-oriented high school or to a vocational school. High school concludes with a set of nationally standardized and externally graded matriculation exams. Though students have a reasonable amount of freedom in choosing the subjects they want to take an exam in, they have to take into account that different higher education programs value matriculation exam grades in different subjects differently.

Higher education is provided by polytechnics, also called universities of applied sciences, and by universities. The former mainly offer bachelor programs, and the latter mainly combined bachelor/master programs. About half of each birth cohort ever enrolls in higher education, with total yearly admissions somewhat larger at polytechnics than at universities. Although it is not uncommon for vocational school graduates to apply to a polytechnic, high school graduates are the largest group of polytechnic applicants.
...
"Higher education applications are extremely competitive, with for example only about one-third of polytechnic applicants being admitted nationally each year. Rejected applicants are likely to reapply, often multiple years, and even admitted applicants often reapply. Re-applications are an important reason why the numbers of applicants per seat are so large. Applicants effectively queue into higher education, likely causing them to be admitted at an unnecessarily old age, and therefore also to graduate at an unnecessarily old age. The 2011 polytechnic applicants on which this study is based for example had on average graduated from high school already two and a half years earlier, and many of them would be older still when they were finally admitted to the higher education program they would eventually graduate from.

"All higher education applications are made to a national clearinghouse. Polytechnic admission decisions are generally made centrally by the clearinghouse itself, while university admission decisions are generally not. In this paper, I analyze the 2011 centralized assignment of high school graduates to Finnish polytechnics. In total, 50,894 high school graduates applied to 16,655 seats in 440 programs, divided over 8 fields.

"The application process starts in March, when applicants can apply to up to four programs in order of preference. Applicants must then choose which entrance exams to prepare for and take, typically in May or June. After the entrance exams have been graded, an admission score is calculated for each application. This score is mainly based on applicants' matriculation exam grade point averages and entrance exam results. The weights assigned to different matriculation exam subjects are typically shared within each field, and entrance exams tend to be shared as well. Extra points are awarded for the first listed choice, as well as for factors like relevant labor market experience. The relative weight of the different admission score components in determining the admission score can be seen in Table 2.

"Based on their submitted preference ordering and on their admission scores, applicants are assigned to programs through a centrally run program-proposing deferred acceptance algorithm, each applicant either being admitted to a single program or not being assigned at all. Admitted applicants then either accept their seat or reject it. A much smaller second round of offers is sent out by the programs themselves to make up for first-round rejections. The second round of the process ends at the start of the fall term in September.
...
"Applicants have multiple reasons to strategize in choosing which programs to apply to. Among others, the fact that applicants receive extra points for their first listed choice implies that they will want to list a program first where they have a chance to actually be admitted. Similarly, the four-program limitation means not only that there may be programs acceptable to the applicant which the applicant is not allowed to list, but also that the applicant will need to use the four allowed applications wisely. Third, the applicant faces a strategic choice in which entrance exams to prepare for and take, typically concentrating all effort on a single application. Fourth, the use of a program-proposing algorithm may in and of itself already give applicants an incentive to strategize."
...
"Though applicants receive good indications of their matriculation exam grades before they apply, and may be aware of previous years' admission score cut-offs, they however necessarily learn their entrance exam scores only after choosing where to apply and which entrance exams to take, adding a considerable degree of uncertainty to their application.
...
"When classifying applicants into thirds based on their program-specific matriculation exam GPA, as many as 54% of top third applicants remain unassigned anywhere. Even using the actual admission score, 34% of top third applicants remain unassigned.
...
"Even if applicants do apply to more than one program, their admission chances are relatively low for programs listed second, third and fourth, with the probability of being assigned to a program being 27% for the program listed first, but only between 3 and 4 per cent for programs listed lower. This is partly due to the extra points given for the first listed program, but is probably also related to applicants' strategic choices on which entrance exams to take. "