Incorporating biology into discrete event simulation models of organ allocation

We describe a discrete event simulation model of the national liver allocation system. This model differs from previous modeling efforts in that it considers the natural history of the disease independently of any particular patient priority scheme, thus allowing an unbiased appraisal of various allocation schemes. We provide the basic structure of the model, which consists of patient and organ generators, a survival module, and a disease progression module. The model provides various outputs such as patient survival, financial cost, and the number of wasted organs. We describe our model of patient survival with and without a transplant. We discuss some difficulties estimating model parameters due to a lack of appropriate medical data, and how these difficulties were overcome. We close with conclusions and directions for further research.