An Update on a Successful Simulation Project: the Unos Liver Allocation Model

The UNOS Liver Allocation Model (ULAM) is a simulation of the cadaveric liver allocation system in the United States. ULAM was created by the United Network for Organ Sharing (UNOS) in collaboration with Pritsker Corporation/Symix Systems, to permit comparison of multiple liver allocation policy proposals so that policies can be tested prior to implementation. ULAM is extremely adaptable, and with it UNOS has been able to respond to varied and complex requests for policy analysis. ULAM has aided UNOS throughout the highly publicized national liver allocation debate, and its use is anticipated for the foreseeable future. The authors believe that ULAM is an excellent example of simulation technology used to resolve national medical policy issues. The success of ULAM, in terms of its ease of use, flexibility of design, and acceptance by the transplant community, has reinforced UNOS’ desire to create other organ allocation models. This paper provides a brief description of ULAM’s structure, and summarizes the evolution of ULAM from 1995 to 2000.