A collaboration between Johns Hopkins and MIT
scientists has mathematically demonstrated that a national
matching program for kidney paired donation, also called
paired kidney exchange, would ensure the best possible
kidney for the greatest number of recipients who have
Kidney paired donation, or KPD, provides organs to
patients who have a willing, designated donor who is not
compatible. A kidney from such a donor is matched to
— and transplanted into — the recipient of a
second incompatible donor-patient pair, and vice versa. The
transplants are performed simultaneously.
The researchers have developed an interactive Web
www.OptimizedMatch.com, that provides more details and
interactive demonstrations of the algorithm and its use in
"Our findings demonstrate that a national pool of
kidney donors and recipients, combined with new
mathematical techniques for sorting through them to find
the best possible organ matches, will not only allow more
people to get the transplants they need but will
dramatically cut health care costs, reduce disruptive and
unnecessary travel for patients and ensure that
transplanted kidneys have the best possible chance of
survival," said Dorry L. Segev, a surgeon at Johns Hopkins
and lead author of a report published in the April 20 issue
of the Journal of the American Medical Association.
"Even if only 7 percent of patients awaiting kidney
transplantation participated in an optimized national KPD
program, the health care system could save as much as $750
million," Segev said.
More than 60,000 people await kidney donation and are
listed on the United Network of Organ Sharing recipient
registry, and nearly one-third of patients with willing
donors are excluded from kidney transplantation because of
blood type and other incompatibilities, according to the
Despite its promise, only 51 patients have received
transplants via paired donation because just a handful of
institutions are performing the procedures based on local
or regional patient databases, added the authors.
"Clearly, a national matching program is the best
solution for incompatible donors and recipients, but for
such a program to be successful we need to make sure that
all patients get the best possible match" Segev said.
Segev, in collaboration with his wife, Sommer E.
Gentry, an applied mathematician at MIT, and other
colleagues developed a new kidney donor matching system, or
algorithm, that uses a technology called optimization. This
technology has already proved successful in facilitating
tasks such as airline scheduling and online driving
directions. They then created a mathematical model that
uses simulated pools of incompatible donor/recipient pairs
to determine if their new matching algorithm might improve
matches that can be found in a small (regional) or large
(national) pool. The researchers compared the optimized
algorithm with the scheme currently used in some centers
and regions. The model included simulated patients from the
general community with characteristics drawn from
distributions describing end-stage kidney disease patients
eligible for kidney transplantation and live donors.
The researchers found that a national optimized
matching algorithm would result in more transplants, better
matches and more transplanted kidneys surviving at five
years when compared with an extension of the currently used
method to a national level. Highly sensitized patients, who
are extremely difficult to match and typically wait almost
seven years for a deceased donor kidney, would benefit
sixfold from a national optimized algorithm (14.1 percent
matched vs. 2.3 percent). Furthermore, the results show
that optimization would dramatically reduce the number of
pairs required to travel (2.9 percent vs. 18.4 percent).
Another benefit of a national KPD model is that
patients and doctors will be able to choose which
priorities are highest for the patients in the system, the
authors added. For example, individual patients can set
their own priorities based on distance they are willing to
travel or on the quality of the kidney matched to them.
Other authors of the report are Daniel S. Warren,
Brigitte Reeb and Robert A. Montgomery, all from Johns
Hopkins. The research was funded by an American Society of
Transplant Surgeons grant and a U.S. Department of Energy
Computational Science Graduate Fellowship.
Hopkins' Comprehensive Transplant Center has had a
kidney paired donation program since 2001. In August 2003,
Johns Hopkins surgeons performed the world's first triple
swap kidney transplant operation, transplanting the kidneys
from three donor and recipient pairs simultaneously. A
second successful triple swap kidney transplant was
performed at Johns Hopkins in March 2004.