Evidence-based development of liver allocation: a review.

Liver transplantation has undergone a rapid evolution from a high-risk experimental procedure to a mainstream therapy for thousands of patients with a wide range of hepatic diseases. Its increasing success has been accompanied by progressive imbalance between organ donor supply and the patients who might benefit. Where demand outstrips supply in transplantation, a system of organ allocation is inevitably required to make the wisest use of the available, but scarce, organs. Early attempts to rationally allocate donor livers were particularly hampered by lack of available and suitable data, leading to imperfect solutions that created or exacerbated inequities in the system. The advent and maturation of evidence-based predictors of waiting list mortality risk led to more objective criteria for liver allocation, aided by the increasing availability of data on large numbers of patients. Until now, the vast majority of allocation systems for liver transplantation have relied on estimation of waiting list mortality. Evidence-based allocation systems that incorporate measures of post-transplant outcomes are conceptually attractive and these transplant benefit-based allocation systems have been developed, modeled, and subjected to computer simulation. Future implementations of benefit-based liver allocation await continued refinement and additional debate in the transplant community.