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Mayo Clinic Proceedings contributors discuss impact of donor organ allocation system

February 07, 2008

ROCHESTER, Minn. -- Liver transplant is a life saving treatment option for people with end-stage liver disease. Unfortunately, the need for donor livers far exceeds the supply. Each year only about one-third of people who need a donor liver will receive one, and some patients die while waiting. In the February issue of Mayo Clinic Proceedings, physicians explore how the current system for allocating donor organs in the United States affects outcomes for patients with end-stage liver disease.

In the United States, the United Network for Organ Sharing (UNOS) oversees the allocation of donor organs. With the goal of giving available donor organs to the most critically-ill transplant candidates, UNOS adopted a scoring system called the Model for End-Stage Liver Disease (MELD) in February 2002. Unlike past evaluation systems, the MELD score de-emphasizes the length of time a patient has been waiting for a donor organ.

A patient's MELD score is calculated from the results of three laboratory tests. Scores range between 6 and 40, with higher numbers reflecting a more urgent need for transplantation. Research has shown that although the donor liver shortage persists, implementing this allocation system has decreased the number of patients who die while waiting for donor organs.

"Early referral to a liver transplant center no longer provides an advantage for organ allocation. However, it is unclear whether it offers other advantages, or if alternative strategies should be developed regarding timing of referral for liver transplant," writes Jaime Aranda-Michel, M.D., a member of the Mayo Clinic Jacksonville liver transplant team and lead researcher for a Mayo study on this topic.

The Mayo study examined the evaluation practices and denial and acceptance criteria for liver transplant used by the Mayo Clinic Jacksonville Transplant Center after the MELD system was implemented.

"Obtaining a clearer understanding of these issues could result in changes in the approach to referrals for liver transplant," writes Dr. Aranda-Michel.

Mayo researchers examined medical records from 555 patients referred for liver transplant at Mayo Clinic Jacksonville Transplant Center from Jan. 1 through Dec. 31, 2005. A transplant selection committee typically determines patient eligibility for liver transplant using a variety of criteria, including a patient's MELD score. From these 555 patients, 260 were accepted for liver transplant at their first review, and 295 (53 percent) were denied. Among those denied for transplant, 150 (51 percent) were considered too early for liver transplant while the rest were excluded due to other medical conditions and psychosocial issues that affected their eligibility. Patients seeking referral for liver transplant often undergo repeated assessments by selection committees, as their eligibility can change over time or following treatment and/or changes in conditions that led to their initial exclusion.

Significance of the findings

According to Dr. Aranda-Michel, the data from the Mayo study suggest that even though the current donor organ allocation system favors the most critically-ill patients, a broad range of patients could benefit from early referral for liver transplant evaluation.

"Our study suggests that early referral for liver transplant evaluation is offers other advantages unrelated to the time patients spend on the liver transplant waiting list. If patients too early for liver transplant were evaluated but not listed, a liver transplant center could initiate management of end-stage liver disease and address psychosocial issues in a subgroup of patients who could also ultimately benefit from liver transplant. Early referral could also lead to the earlier detection and treatment of liver cancer tumors called hepatocellular carcinomas that accompany some forms of chronic liver disease. If these tumors become too large, they can make a patient ineligible for transplant," says Dr. Aranda-Michel.

In an editorial that follows, author Gennaro Selvaggi, M.D., from Miami Transplant Institute at the University of Miami, agrees that while the MELD system has proven to be valuable, those who are responsible for placing patients on transplant lists face many challenges.

"One could argue that keeping a long list of active patients with low MELD scores could burden the system. However, many patients can experience a sudden decompensation of their liver disease, which would rapidly increase their MELD score," writes Dr. Selvaggi.

"In the end, the most important concept advanced by Aranda-Michel is that patients should be referred early and followed up by a team of liver transplant specialists," writes Dr. Selvaggi.

Mayo Clinic