Model for end‐stage liver disease exceptions: A common problem

In order to ensure access of organs to candidates with certain disease states unfairly underprioritized by the Model for End-Stage Liver Disease (MELD) score, United Network for Organ Sharing (UNOS) instituted a policy of “exception” priority wherein syndromes with underappreciated transplant urgency or mortality risks receive exception MELD points above the calculated MELD score. The explicit goal of this system is to approximate as closely as possible the predicted mortality risk defined by the granted exception MELD score to the actual risks of the patient. These can be standard exceptions, where protocol increases are automatically applied to patients meeting criteria (eg, hepatocellular carcinoma [HCC]) or nonstandard exceptions, which require written applications to be approved by a regional review process. With standard exceptions, the US allocation system allows patients with low priority despite quantifiable risks to undergo transplant in a timely fashion and thereby enhance equity of the entire system. In addition to HCC, hepatopulmonary syndrome, cholangiocarcinoma, familial amyloid polyneuropathy, cystic fibrosis, and portopulmonary hypertension are eligible for standardized exceptions under the MELD allocation system. Equating MELD exception scores to risk of death is difficult. Past policy has raised concerns about exacerbating organ scarcity and contributing to a nationwide inflation of MELD at transplant. For example, HCC has been the most frequent indication for extra MELD points. Multiple analyses have suggested overprioritization of HCC patients who enjoyed shorter waiting times and lower wait-list dropout rates. There have subsequently been several iterations of HCC exception priority policy to reduce awarded MELD exception points. Meanwhile, use of exception points for liver transplant has increased. The problem extends beyond HCC. Patients waitlisted between 2002 and 2010 with MELD exception points for any condition were less than half as likely to die on the waiting list compared with patients without exceptions with equivalent listing priority. These rates include nonstandard exceptions, which lack standardized criteria, guidelines for implementation, and often objective justification. For example, primary sclerosing cholangitis (PSC) had often received exception points for increased wait-list mortality, yet data suggest no such increased risk. UNOS policy efforts are underway to try to address MELD exceptions and notably include continued review of HCC prioritization and planned formation of a national review board to improve uniformity of nonstandard exceptions across regions, approved June 2017. In this issue of Liver Transplantation, Umgelter et al. report a retrospective analysis comparing patients with exception priority versus those without in the Eurotransplant International Foundation. Eurotransplant supports organ allocation for Austria, Belgium, Croatia, Germany, Hungary, Luxembourg, the Netherlands, and Slovenia. Like UNOS, Eurotransplant uses the MELD score for allocation and has a system of standard and nonstandard exceptions. Notable differences include standard exceptions for biliary sepsis/secondary sclerosing cholangitis, polycystic liver disease, and PSC. By and large, initial exception score and protocol increases are similar to UNOS with the notable exception of HCC with continued prioritization similar to UNOS policy prior to 2015. The analysis included adult patients wait-listed for deceased liver donation between December 2006 and December 2015, and it focused on Belgium, the Netherlands, and Germany because these countries allocate organs to individual patients rather than solely to centers. Abbreviations: HCC, hepatocellular carcinoma; MELD, Model for End-Stage Liver Disease; PSC, primary sclerosing cholangitis; UNOS, United Network for Organ Sharing.