Although more than 100,000 people are on the national transplant waiting list in the U.S., thousands of donated kidneys are discarded each year, often because they’re slightly older, with fewer years of remaining function.
Researchers at Virginia Tech and other institutions led a study of a potential redesign of the national kidney transplant system that matches older organs more efficiently with patients over 65. Their results, published in the prestigious journal Management Science , found that a new program could result in more than 900 additional kidney transplants each year, potentially preventing more than 190 deaths.
The research examines a voluntary approach known as a targeted priority mechanism. Inspired by the Eurotransplant Senior Program, it targets waitlisted candidates aged 65 or older by offering them kidneys that others consider “marginal” — for instance, kidneys from older adults. Patients who agree to accept harder-to-place kidneys are prioritized and moved to the front of the waiting list, in exchange for giving up access to kidneys outside of that group.
“This encourages more efficient matching without forcing patients to accept organ offers or requiring a complete redesign of the current allocation system,” said Sait Tunc , assistant professor in the Grado Department of Industrial and Systems Engineering , who led the multi-institutional research team. “This program is not only beneficial to those who participate, but also to younger patients who are not eligible for it, because higher quality organs can be better matched to patients with higher post-transplant life expectancy. It's almost like a win-win situation.”
The kidney transplantation system presently faces a supply-demand gap, with patients waiting an average of five years for a transplant. Simultaneously, approximately 20 percent of donated kidneys never find a recipient because of inefficient matching among organs, patients, and transplant centers, as well as provider biases.
“Providers that accept organs often make decisions about when to accept an offer based on heuristics that may be based on concrete data, but could also include assumptions and biases specific to them and their clinical experience,” said Matthew J. Ellis, medical director of the Kidney and Pancreas Transplant Programs at Duke University School of Medicine. “This results in many kidneys that will never be used and contributes to the supply-and-demand misalignment.”
The research combines mathematical analysis of patient choices with a sophisticated computer simulation of the U.S. kidney allocation system that uses machine learning and predictive models trained on historical transplantation data. The simulation analyzes matching techniques and predicts how participation and offer acceptance could change with this voluntary program’s rules.
The projected impact is immense. Rather than waiting multiple years, patients could receive a transplant within a few months or less. The potential benefits extend beyond program participants. By improving access to harder-to-place kidneys for willing older patients, kidneys expected to function longer become available to other patients. The simulated program model showed that prioritizing one group does not have to come at another’s expense when program rules are carefully crafted and flexible.
The study was funded by Tunc’s 2024 National Science Foundation CAREER Award . The second phase of the research will focus on initial policy discussions with transplant professionals, as well as practical program designs for clinicians and patients to evaluate.
"The Management Science article is great to bring discussions into our community and establish that what we have done is theoretically rigorous," Tunc said. "But the next step is to bring this to the transplant community."
With the publication providing a credible springboard, the research team hopes to translate the redesigned transplant system to clinical practice through clinically based journals and working groups within the United Network for Organ Sharing, a nonprofit organization that administers the U.S. organ transplantation system.
Original study : DOI 10.1287/mnsc.2024.05724
Management Science
Targeted Priority Mechanisms in Transplantation: Incentivizing, Not Enforcing, Efficient Matching of Organs
5-Aug-2026