'Redistricting' Considered for Liver Donor Maps

Researchers report that the existing distribution model of organs for liver transplants is unbalanced and depends upon longstanding relationships among medical centers. Organ donor advocates are calling for a change in the allocation process.

Organ donor advocates want to copy the mathematical formulas that draw boundaries for political maps and zoning districts and use them to create a more equitable allocation of transplanted livers from deceased donors.

"Currently the geographic disparity for access to livers in this country is great," says David C. Mulligan, MD, director of Surgical Transplantation at Mayo Clinic Hospital in Phoenix, AZ. "We need to find better ways to improve our system of allocation to reduce this disparity so that in the end, access to liver transplants will be the same or as close to the same as possible no matter where you live in this country."

Geography can mean the difference between a 10% – 90% chance of dying while on a waiting list for a donor liver, researchers say. "The existing system is based on the geography of where a handful of centers that were performing liver transplantation were located," says Mulligan, who is also chair of the liver committee for the Organ Procurement and Transplantation Network/United Network for Organ Sharing.

Researchers at Johns Hopkins University School of Medicine reported this month that the existing "unbalanced" distribution model depends upon the longstanding relationships among medical centers.

Mulligan agrees.

"When liver transplantation was first developed in this country, the transplants were done at a handful of centers, five or six centers started the whole process," he says. "They were distributed across the country from Pittsburgh and Dallas and Los Angeles and Omaha NE so each of these programs as they were beginning to develop needed to try to determine where organs could potentially come from."

"They knew that the cold storage time had an impact on the outcome of the transplant so they didn't want to be pulling organs from one part of the country in those days and putting them in on the other coast into their patients. They tried to develop systems or regions so that organs when they were recovered by the organ procurement organizations as they were being developed could get placed into the patients on the transplant lists that were closest in proximity to get the best possible outcome," Mulligan explains.

"As the success of organ transplant continued, we could see that the ability for preserving these organs improved, the ability to do the transplants improved, the outcomes improved, and more and more centers started to perform liver transplants and there became a need for a more developed and complex way of trying to approve the allocation for these organs to get to their patients."  

Dorry L. Segev, MD, an associate professor of surgery and epidemiology at the Johns Hopkins University School of Medicine is the author of a report that examines the use of mathematical formulas to create a more equitable distribution, which he calls "gerrymandering for the public good."

"We have applied to transplantation the same math used for political redistricting, school assignments, wildlife preservation and zoning issues," Segev said in a media release. His report was published this month online in the American Journal of Transplantation.

Mulligan says he supports the recommendations from the Johns Hopkins study and that the OPTN/UNOS liver committee is reviewing redistribution models. Now, however, he says the biggest roadblock towards a coordinated national system may be turf wars among transplants centers.

"I would love to say that everyone is on the page. We all agree that all of the transplant physicians and surgeons and organ procurement organizations want what is best for their patients. The biggest roadblock is getting buy-in for thinking in a different parameter, taking a step back and saying what is best for all patients in the United States," Mulligan says.  

"The big piece is to get everyone to look at the big picture, to look at all patients in the country and not just their own. Because in areas where there is a huge disparity and long waiting times in liver transplants those centers are going to be excited to see a new opportunity for their patients to get organs more effectively and efficiently."

"On the flip side," Mulligan says, "centers and regions in the country that have very productive organ procurement organizations and a lot of organ donation and populations of donors who are very motivated, those centers look at this type of a proposal as a hurt to their patients, that their patients are now going to have to wait longer because they are sharing with other centers."

If it were up to him, Mulligan says he'd like to see a nationally coordinated allocation plan for donated livers in place within the next few months. "But realistically, I would like to see the first step of Phase 1 of a redistricting plan in place and out for public comment and going forward with board approval for implementation within the next two years," he says. "That is going to be a bold undertaking, but that is what we are trying to achieve. It may take longer, but I am going to do everything possible to make it as short a time as possible as I can."

If the coordinated effort works for donated livers, Mulligan says it could serve as a distribution model for other donated organs, which often have their own unique distribution networks.  

"If this is successful in liver [allocations] we will need to study to see if there is something we can do to improve the way hearts are distributed, because they do a whole different system," he says. "They are distributed based on circle distribution from each donor hospital, how many hundreds of miles they go out and how sick they are. We would look to applying these types of mathematical models to all organs and maybe adjust the models to factors that are necessary for each of these organs to make the process better."