Study: Transplant Liver Allocation System Disadvantages Children
A new study says the national system that allocates livers to transplant candidates might inadvertently give adults an advantage over children.
The research was published online in the journal JAMA Pediatrics.
All else being equal, adults and children awaiting liver transplants are prioritized based on two similar 40-point scoring systems that reflect short-term risk of death: the Model for End-stage Liver Disease (MELD) for candidates 12 years old and older and the Pediatric End-stage Liver Disease (PELD) for children aged 11 and younger.
These "medical urgency formulas," which are based on biomarkers of liver function, perform well when comparing children and adults to their peers.
But setting a child's PELD score against an adult's MELD score can produce unfair outcomes, says the study, because the child formula underestimates mortality by up to 17 percent.
"The trouble is, when there's a tie between an adult and a child, the scores say, 'Oh, they have the same risk of death.' But, in fact, the child has a much higher risk of death," said co-author Dr. Mark Roberts of University of Pittsburgh.
Doctors can raise patients' scores by asking for exception points, but Roberts and his colleagues contend that their results call for more systemic change — either in the PELD system itself or in how it is implemented.
PELD and MELD scores have been used since 2002 as a more objective and transparent alternative to earlier, less consistent systems.
"It was all designed with the intention of producing a fair, reasonable and un-gameable system. It's just that I think we can do better now," said Roberts.
The United Network for Organ Sharing (UNOS), which manages organ transplants in the U.S., also prioritizes liver matches by proximity to the organ harvesting site, favoring first local, then regional and finally national candidates. This criterion is based on the limited window in which the donor organ remains viable.
The Organ Procurement and Transplantation Network, the public-private partnership that oversees UNOS, acknowledges that this system can create disparities for remote patients in smaller communities.
It can also mean that local adults receive priority over children located father away.
A 2017 study in the journal Gastroenterology described a five-year period in which 316 children died, or were removed from transplant lists for being too ill, while 1,667 adults received transplants of child livers.
That paper's lead author, Dr. Evelyn K. Hsu of University of Washington School of Medicine, Seattle, co-wrote an editorial commenting on the "PNAS Pediatrics" study. In it, she described what she calls a paradox: the fact that enough child livers exist to meet the needs of children, but "go to adults locally and regionally rather than to critically ill children nationally."
"Approximately 500 deceased-donor liver transplants are performed each year in children in the United States, a number that has remained constant over the past two decades, while the number of adults who receive transplants is more than 10-fold higher and is increasing by 10 percent per year," she wrote.
Most of this increase stems from the growing senior population, but that fact does not alter the underlying problem.
"In the setting of a limited supply of livers for transplant, the central issue of whom to prioritize for transplant and how to do so remains."