Model for end‐stage liver disease (MELD) for liver allocation: A 5‐year score card

Liver allocation has always been controversial, mostly because the donor supply is inadequate to provide treatment for all candidates who can potentially derive benefit from the liver transplantation (LT) procedure. In the late 1990s, most of the controversy centered around extreme differences in waiting time among LT candidates in different geographic regions and the use of waiting time and other subjective variables that did not necessarily reflect patient disease to assign priority. In response to these concerns, the Institute of Medicine report recommended,1 and the Department of Health and Human Services Final Rule for the Organ Procurement and Transplantation Network (OPTN) stipulated,2 that liver allocation should be based on objective medical criteria with a de-emphasis on waiting time. On the basis of the Institute of Medicine report1 and other studies indicating that mortality risk was a much more appropriate measure for ranking waiting LT candidates,3 policymakers selected the Model for End-Stage Liver Disease (MELD) score as the measure of disease severity because it utilized objective, reproducible, patient-based variables only, and because it was validated as an accurate predictor of short-term mortality for most adult patients with chronic liver disease.4 The Pediatric End-Stage Liver Disease (PELD) score was developed as a measure of mortality for children with end-stage liver disease along similar lines.5 The OPTN formulated the new liver allocation policy to incorporate the MELD/PELD scores as a disease severity scale and virtually eliminated waiting time as a prioritization variable in the system.6 During the MELD policy genesis, the developers realized that not all candidates for LT suffer from diseases that carry an immediate mortality risk and that these patients would not be well served by a priority system based solely on a mortality risk endpoint. Patients with hepatocellular cancer (HCC) are the largest such group because many of these LT candidates have a risk of their malignancy progressing beyond a curable stage that is much greater than their immediate risk of dying of intrinsic liver failure.7 For this reason, a peer review system was developed to allow centers to request extra priority for patients with these so-called exceptional diagnoses. The OPTN implemented this MELD/PELD-based system for liver allocation on February 27, 2002. In comparison with the year prior to MELD allocation, during the first year under the MELD system, there was a reduction in new LT waiting list registrations with the largest reductions seen in new registrants with low MELD/ PELD scores, a reduction in the waiting list death rate, and an increase in deceased donor transplants. The reduction in waiting list mortality and increase in transplantation rates were evenly distributed across demographic and liver disease etiology strata, with some variation across geographic variables. Early patient and graft survival after deceased donor LT was not changed.8 Over the ensuing 5 years, much attention has been focused on this new system, with more than 400 titles in the literature mentioning MELD and liver allocation. Many other countries have adopted, or are considering adopting, MELD-based liver allocation policies using many of the same principles developed by the OPTN.9 At this point in time, it is appropriate to assess the status of MELD-based liver allocation in the United States and identify areas for future consideration. One of the most significant changes brought on by MELD is that patients and the system can be much more easily measured. By the removal of subjective variables, patients’ natural history, physician behavior, and the effect that these variables have on the overall results of the system can be more readily compared and quantified. This is essential for any critical assessment of healthcare delivery systems and allows for the definition of metrics by which such a system is to be judged. Although many Abbreviations: AA, African American; BA, biliary atresia; BCS, Budd-Chiari syndrome; BMI, body mass index; DSA, donor service area; FEV1, forced expiratory volume at 1 second; HCC, hepatocellular cancer; ICP, intracranial pressure; LT, liver transplantation; MAP, mean arterial pressure; MELD, Model for End-Stage Liver Disease; MPAP, mean pulmonary artery pressure; OPO, organ procurement organization; OPTN, Organ Procurement and Transplantation Network; PELD, Pediatric End-Stage Liver Disease; PVR, pulmonary vascular resistance; RRB, regional review board; RV, right ventricle; TIPS, transjugular intrahepatic portosystemic shunt; UNOS, United Network for Organ Sharing. From the Division of Transplantation, Tufts–New England Medical Center, Boston, MA. Received September 6, 2007; accepted October 29, 2007. Address reprint requests to: Richard B. Freeman Jr, M.D., Division of Transplantation, Box 40, Tufts–New England Medical Center, 750 Washington Street, Boston, MA 02111. E-mail: rfreeman@tufts-nemc.org; fax: 617-636-8228. Copyright © 2007 by the American Association for the Study of Liver Diseases. Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hep.22135 Potential conflict of interest: Nothing to report.