ROSEMONT, Ill.—A proposal to use a complex mathematical formula to generate major transformation in the way donated livers are allocated in the U.S. was again met with criticism by the liver transplant community.
Attendees at a liver forum held Monday in a Chicago suburb remained split on the plan, which was first shared by the United Network for Organ Sharing about a year ago. Some members called the emphasis on allocation the low-hanging fruit and argued that UNOS was ignoring other pressing liver transplant issues.
UNOS told attendees it is weighing the concerns, but also said the current system has resulted in glaring geographic disparities and wait times so long in some regions that patients with private insurance have to move to other states for better chances at obtaining organs.
“We realize the magnitude of change,” said Dr. David Mulligan, chair of the group's liver and intestinal organ transplantation committee. “But the goal is to create something that makes sense.”
The framework proposed last June included narrowing the current number of allocation districts from 11 to as few as four. It also included use of two statistical tools: one commonly used to establish election districts and another used by the airline industry to boost travel efficiency.
Redistricting would allow livers to flow from areas with greater-than-expected eligible deaths and fewer-than-expected listings to areas with the opposite, explained Sommer Gentry, associate professor of mathematics with the U.S. Naval Academy.
“Liver allocation should change whenever it becomes apparent that geographic disparities have grown to a really unacceptable level,” said Gentry, who helped UNOS with the mathematical designs. “We've reached that point. That's why we're here.”
Gentry and was one of more than 20 panelist presenting new data to the forum of more than 400 attendees. Other panelists urged UNOS to hold off on implementing the strategy.
For example, Sanjay Mehrotra, a professor of industrial engineering and management sciences at Northwestern University who has done previous work on kidney allocation, discussed principles for optimizing a robust modeling redesign.
Mehrotra suggested that other known disparities in liver transplantation—such as varying donation rates and issues with the score used to determine the severity of a patients' disease—could lead to unintended outcomes, such as skewed supply and demand. “There is insufficient evidence and scientific validation of the current proposal,” he said.
UNOS plans to announce by Tuesday afternoon the next step for the proposal. If the response from the audience is any indication, the group has much to consider. Surgeons, mathematicians, clinicians and others cued up at the three microphones spanning the conference room for the Q&A following each round of presentations.
“Allocation cannot be based on statistics; we have to use common sense,” said one attendee. A strategic program for addressing the other liver transplant disparities needs to be addressed simultaneously with any redistricting, said others, including a transplant surgeon from Iowa who added, “If we don't know where we are going, any path will get us there.” Because transformational restructuring takes time, it is best to use the current opportunity to come up with a model that “makes intellectual sense” rather than “a system based on statistically fulfilling artificial boundaries,” one clinician said.
Mulligan, the chairman of the UNOS committee, said the current dialogue is prompting the thoughtful consideration needed to make the allocation model one that will be effective over the long term.
He also said there is nothing artificial about the numbers. The chance of receiving a liver in three months is 12% in one part of the country and 83% in another. “Those are real numbers- not modeled, not hypothetical. That's real.” he said. “We have a real disparity issue. We have to start changing how we do things.”
