We present the ELAS simulator, a discrete event simulator built for the Eurotransplant (ET) Liver Allocation System (ELAS). Eurotransplant uses ELAS to allocate deceased donor livers in eight European countries. The simulator is made publicly available to be transparent on which model Eurotransplant uses to evaluate liver allocation policies, and to facilitate collaborations with policymakers, scientists and other stakeholders in evaluating alternative liver allocation policies. This paper describes the design and modules of the ELAS simulator. One of the included modules is the obligation module, which is instrumental in ensuring that international cooperation in liver allocation benefits all ET member countries. By default, the ELAS simulator simulates liver allocation according to the actual ET allocation rules. Stochastic processes, such as graft offer acceptance behavior and listing for a repeat transplantation, are approximated with statistical models which were calibrated to data from the ET registry. We validate the ELAS simulator by comparing simulated waitlist outcomes to historically observed waitlist outcomes between 2016 and 2019. The modular design of the ELAS simulator gives end users maximal control over the rules and assumptions under which ET liver allocation is simulated, which makes the simulator useful for policy evaluation. We illustrate this with two clinically motivated case studies, for which we collaborated with hepatologists and transplantation surgeons from two liver advisory committees affiliated with Eurotransplant.

翻译：本文介绍了ELAS模拟器，这是一个为欧洲移植（ET）肝脏分配系统（ELAS）构建的离散事件模拟器。欧洲移植组织利用ELAS在八个欧洲国家分配已故捐赠者的肝脏。该模拟器已公开发布，旨在透明展示欧洲移植组织用于评估肝脏分配政策的模型，并促进与政策制定者、科学家及其他利益相关方在评估替代性肝脏分配政策方面的合作。本文详细阐述了ELAS模拟器的设计架构与功能模块。其中包含的义务模块对于确保肝脏分配国际合作惠及所有ET成员国具有关键作用。默认配置下，ELAS模拟器按照ET现行分配规则进行肝脏分配模拟。移植器官接受行为、再次移植登记等随机过程通过统计模型进行近似，这些模型已根据ET登记处数据完成校准。我们通过对比2016年至2019年间模拟等待名单结果与历史观测数据，对ELAS模拟器进行了有效性验证。该模拟器的模块化设计赋予终端用户对ET肝脏分配模拟规则与假设的最大控制权，使其成为政策评估的有效工具。我们通过与欧洲移植组织下属两个肝脏咨询委员会的肝病学家和移植外科医生合作开展的两项临床案例研究，具体展示了该模拟器的应用价值。