After nine years of steps forward, back, and forward again, the Organ Procurement and Transplantation Network (OPTN) Kidney Transplantation Committee has proposed a revamping of the deceased-donor kidney allocation system that makes calculated adjustments while avoiding some of the more dramatic, and contentious, changes previously debated.
“What we're trying to do is make better use of the organs we have available,” said John Friedewald, MD, Chair of the Kidney Transplantation Committee and Associate Professor of Medicine and Surgery at Northwestern University Feinberg School of Medicine, in a phone interview. “Unfortunately, with the tremendous shortage of organs, nothing is going to please everybody.
“This was a very careful balance, after many, many iterations of trying different things, to come up with the best solution to increase the amount of life we can get from these kidneys but, at the same time, maintain access for all patients, particularly of different age groups but also of different racial groups.”
One way the committee hopes to accomplish these goals is by matching the top 20% of kidneys with the 20% of candidates estimated to live the longest after transplantation.
“Through a fairly small change affecting really only a fairly small group of patients, we're getting a huge life-year benefit,” Dr. Friedewald said.
The Top 20 Percent
Under the proposal, the top 20% of kidneys and candidates would be identified using two metrics—the kidney donor profile index (KDPI) and estimated posttransplant survival (EPTS), respectively.
The KDPI is a continuous scale based on donor age, height, weight, ethnicity, history of hypertension, history of diabetes, cause of death, serum creatinine, hepatitis C virus status, and donation after circulatory death status. The lower the KDPI, the better the estimated donor quality.
This index would replace the dichotomous system that currently classifies kidneys as coming from standard criteria donors (SCDs) or expanded criteria donors (ECDs). ECDs are donors older than 60 or donors age 50 to 59 who also fulfill two of the following criteria: hypertension, creatinine greater than 1.5 mg/dL, or death from cerebral vascular accident.
“The current system of looking at kidneys as either standard or expanded has been interpreted by many people as good kidneys and bad kidneys,” said Michael Shapiro, MD, transplant surgeon and Director of Surgical Education at Hackensack University Medical Center, in a phone interview. “It's hard to sell kidneys in the category of ‘bad kidneys,’ even though there are many SCD kidneys that aren't as good as many ECD kidneys.
“The donor profile index will give people a much more realistic view of what sort of kidneys they're looking at, and that might help bring some reality to which kidney is going to which recipient.”
Dr. Shapiro has been directly and indirectly involved with the proposal, serving on the Kidney Transplantation Committee in the middle of the policy's development and on the Ethics Committee throughout the whole process.
Posttransplant survival is estimated using four factors that are available in the OPTN database, clinically relevant, statistically significant, and objective, the proposal noted: candidate age, length of time on dialysis, prior transplant of any organ, and diabetes status.
“The estimated posttransplant survival model is based on transplant patients and waiting lists from several years ago,” said Richard B. Freeman, MD, in a phone interview. Dr. Freeman, who is Chair of the Department of Surgery at the Geisel School of Medicine at Dartmouth, reviewed the allocation proposal during his term on the Organ Procurement and Transplantation Network/United Network for Organ Sharing Board of Directors. “The question is, is it going to work for future patients?
“The other thing that's important to know is that age is really the main determinant in this estimated posttransplant survival, and the previous suggestions for changing the allocation system basically were shot down, if you will, because age was felt to be an unfair or a discriminatory variable to use in the allocation system. If you take age out of the equation, the estimated posttransplant survival time now has no ability to predict.”
As Good as It Gets
The proposal reflects a “fundamental change in organ allocation philosophy,” Dr. Freeman said.
“This is a policy that says that the length of function of a kidney takes first priority over the potential recipient. We decide which are the really good kidneys first, and then assign them to the really good recipients—the ones most likely to survive a long time.
“That is the opposite of the way all other organ allocation is done, where we rank recipients first and assign organs to recipients. … It's OK to do it the other way around, but I don't think that we've really had that debate.”
For Robert S. Gaston, MD, the proposed update seeks to reset the balance. Dr. Gaston, who was not involved in the development of the policy proposal, is Past President of the American Society of Transplantation, as well as Endowed Professor of Transplant Nephrology and Medical Director of Kidney and Pancreas Transplantation at the University of Alabama at Birmingham.
“The current proposal is a compromise,” he said in a phone interview. “The pendulum had swung too far to an equity-based system and needed to swing back to where some projection of outcomes of which recipient would do best with a given kidney comes back into the equation.
“This proposal does that, and it does it in a way that should increase the efficiency of the system. There will be some sacrifice of equity, but equity remains a major emphasis of the new system as well. It's about as good as I can envision given all the demands on the allocation system.”
Time to Wait
Waiting time remains a key component in the proposal. Unlike the current system, under which waiting time only begins to accrue after transplant listing, candidates would receive credit for any time spent on dialysis before they were added to the list.
“This proposed change is expected to increase the transplant rate for underserved (often ethnic minority) populations who may not receive adequate information to pursue transplant at the time of dialysis initiation and thus may be added to the wait list long after their ESRD [end-stage renal disease] diagnosis,” the proposal noted.
The national median waiting time for deceased donor kidney transplantation is highest for blood type B candidates. The potential new allocation system would address that disparity by allowing those who have that blood type and certain clinical characteristics to accept kidneys from donors with blood type A2 or A2B, an approach that has already shown success in individual organ procurement organizations.
In terms of sensitization, the proposed system would create a sliding scale of additional priority for candidates with a calculated panel reactive antibody score of 20% or higher. There also would be broader sharing for extremely highly sensitized candidates.
“Highly sensitized patients have a really difficult time finding a kidney that they're a good match with, and throwing a larger net across a larger area of the country is a good thing and actually will help get those patients transplanted,” Dr. Freeman said.
“The way blood type is being handled is excellent.”
Proof of Principle
The proposal is open for public comment until Dec. 14, and it will be considered by the Board of Directors in June 2013.
While the proposed system is, in all likelihood, a step in the right direction, the root of the organ allocation problem remains, Dr. Gaston said.
“No matter how you devise an allocation system, someone's going to win, and someone's going to lose,” he said. “The solution has to be more organs, not parsing them differently, even though parsing them differently than we always have may be of overall benefit to the population.”
The potential changes are estimated to result in an additional 8,380 life years achieved annually from the current pool of deceased donor kidneys.
“Although that may be a relatively short amount for each individual patient, it's not trivial,” Dr. Shapiro said. “I look at it as a proof of principle that will demonstrate that this sort of a system can work with kidneys.
“Then the Kidney Committee, although it's going to take a number of years to collect the data to show what effect it's had, can then revise it, improve it, convince the public that it's the right way to go.
“Kidneys are a public good; they belong to society. Society has to believe that what we're doing is the right thing.”
Listen In Online
Tune into the Nephrology Times website at http://bit.ly/NTPodcasts to hear John Friedewald, MD, discuss the proposed changes to how deceased donor kidneys are allocated.
© 2012 Lippincott Williams & Wilkins, Inc.