SEATTLE — The introduction of “MELD/PELD” 3 years ago was a start, but the liver allocation system is continually undergoing adjustments and refinements in an effort to improve outcomes, said Michael R. Lucey, M.D., at the annual meeting of the American Transplant Congress.
The Model for End-Stage Liver Disease (MELD) and Pediatric End-Stage Liver Disease (PELD) are numeric scales that in 2002 replaced the former system used for liver allocation. Both scores are based on a patient's risk of dying while waiting for a liver transplant, and both use objective and verifiable medical data. The higher the MELD or PELD score, the greater the risk of dying from liver disease.
The MELD score uses a mathematical formula based on serum creatinine levels, bilirubin levels, and international normalized ratio. A patient's score can range from 6 to 40. In the event of a liver becoming available to two patients with the same MELD score and blood type, time on the waiting list becomes the deciding factor. In the first year of utilizing MELD scores, the median score of patients who received livers was 18 to 20, with a few spikes to 24 and 27, said Dr. Lucey.
Before the implementation of the MELD/PELD system, there were large disparities in waiting times across geographic regions, as well as difficulties in prioritizing patients.
While the situation has improved, there are still regional variations, said Dr. Lucey, chief of gastroenterology and hepatology at the University of Wisconsin, Madison.
“We have 11 regions and there are regional variations in mean MELD scores, from a high point of 27 to low point of 20,” he said.
In some organ procurement organizations (OPOs), no patients with a MELD of less than 10 received a transplant. Yet in others, as many as 17 or 18 patients whose MELD score was below 10 received a liver transplant.
“So the MELD system demonstrates that not only are there regional variations, but variations between OPOs,” said Dr. Lucey at the meeting, which was cosponsored by the American Society of Transplantation and the American Society of Transplant Surgeons.
One analysis showed that the size of the OPO was associated with how the MELD score was implemented.
It found a significant disparity in MELD scores in liver transplant recipients in small versus large OPOs. Fewer transplant recipients in small OPOs had severe liver disease, as evidenced by MELD scores below 24, he said.
“The smaller OPOs tend to transplant patients who are less severely ill,” said Dr. Lucey.
“There are distinct practices across the country and between OPOs, [although] one of the priorities of MELD was to make geographic distinctions less important in organ allocation.”
This disparity, he added, does not reflect the stated goals of the current allocation policy, which is to distribute livers according to a patient's medical need, rather than to keep organs in the local procurement area.
Patients awaiting livers used to be ranked as status 1, 2A, 2B, and 3, according to the severity of their current disease. The status 1 category has remained in place as the highest priority for receiving an organ and is not affected by the MELD or PELD scores.
A high number of pediatric patients were being transplanted at stage 1 before PELD, with half of them at status 1 and 23% at status 1 by exception.
“But since PELD, there has been a minor reduction in the total number of status 1 transplants, but an increase in those getting status 1 transplants by exception,” said Dr. Lucey. “This calls for a review.”
Another issue is that more than half of the transplant candidates are listed with PELD scores of less than 10, and many such patients are being transplanted. It is important to find out what this means, he explained.
“Status 1 has been redefined for PELD, and we will have to see if stricter rules to define status 1 have had an impact—and an impact that we want,” he said.
MELD and PELD have made it easier to audit the practice of liver transplantation, Dr. Lucey concluded.
“They facilitate data-driven changes in policy and practice and, finally, allow for subsequent auditing after the changes are made, with continuing revisions as appear appropriate.”