Where you live in the United States plays a big role in how long you might wait for a much-needed liver transplant. Patients with liver failure and would-be donors are not distributed evenly around the country. And the nation is divided into 11 transplant regions that have wide variations in patients and available organs, between regions and within them.
McGowan Institute for Regenerative Medicine
affiliated faculty member Mark Roberts, MD, MPP (pictured), Chair of Health Policy and Management at University of Pittburgh’s Graduate School of Public Health, and colleagues address these issues and suggest solutions in their publication “Maximizing the Efficiency of the U.S. Liver Allocation System Through Region Design.”
Dr. Roberts and his team notes cadaveric liver transplantation is the only viable therapy for end-stage liver disease patients without a living donor. However, this type of transplantation is hindered in the United States by donor scarcity and rapid viability decay. Given these difficulties, the current U.S. liver allocation policy balances allocation likelihood and geographic proximity by allocating cadaveric livers hierarchically.
In the current system, as reported by Lauran Neergaard , Associated Press Medical Writer, a donated liver is offered first to the sickest patients in the local transplant center, and if there's no good match, then to the sickest patients throughout that transplant region. If there's still no good match, the liver can go to someone who's not as sick - rather than to someone sicker in the next transplant region.
In their report, the Pitt’s researchers consider the problem of maximizing the efficiency of intraregional transplants through the redesign of liver allocation regions. They formulate the problem as a set partitioning problem that clusters organ procurement organizations into regions. They develop an estimate of viability-adjusted intraregional transplants to capture the trade-off between large and small regions. The team utilizes branch and price because the set partitioning formulation includes too many potential regions to handle explicitly. They formulate the pricing problem as a mixed-integer program and design a geographic-decomposition heuristic to generate promising columns quickly.
Because the optimal solution depends on the design of geographic decomposition, Dr. Roberts and his colleagues develop an iterative procedure that integrates branch and price with local search to alleviate this dependency. Finally, they present computational studies that show the benefit of region redesign and the efficacy of their solution approach. The team’s carefully calibrated test instances can be solved within a reasonable amount of time, and the resulting region designs yield a noticeable improvement over the current configuration.
The researchers said their findings show statistical modeling can be beneficial.
"We wanted to show that just by rearranging which (organ procurement organizations) are in which regions, we could make things better," said Dr. Roberts. "We could transplant more organs."
Illustration: McGowan Institute for Regenerative Medicine.
Pittsburgh Tribune-Review (02/25/11)
Bio: Dr. Mark Roberts
Abstract (Management Science; Vol. 56, No. 12, December 2010, pp. 2111-2122.)