AitF: Algorithms and Mechanisms for Kidney Exchange

Carnegie Mellon University, Pittsburgh PA

Investigators

Abstract

Severe cases of renal failure require kidney transplantation. But the demand for kidneys is huge while the supply is quite limited. Even when a willing donor is found, several hurdles must be cleared before transplantation can take place. Enter kidney exchange, the idea that patients can exchange willing but incompatible donors. In its most basic form ? 2-way exchanges ? two patient-donor pairs swap kidneys, that is, the first donor donates to the second patient and the second donor to the first patient. However, exchanges along longer cycles and even chains are also taking place. In recent years several kidney exchange programs have become operational, building on the work of economists and computer scientists. And while significant progress has already been made, computer science has an even bigger role to play in kidney exchange research. Indeed, the theme of this proposal is that challenges in kidney exchange give rise to a wealth of exciting theoretical questions. Moreover, solving these problems matters: These problems are important to the design and optimization of real-world kidney exchange programs. An overarching goal of this proposal is to narrow the gap between the theory and practice of kidney exchange. The proposed research will incorporate elements such as 3-way exchanges, weighted edges, and chains initiated by altruistic donors into existing work and develop new models that ? while still abstractions of reality ? are able to distill the essence of practical kidney exchange challenges. The project can therefore impact the evolution of kidney exchange programs, which are still in their infancy. In more detail, the project focuses on two main research directions: 1. Dealing with incentives: Transplant centers care foremost about their own patients. Thus if the individual transplant centers cannot each be confident that their own patients will fare at least as well if they participate in the exchange than if they do not, then they may not join. Even more subtly, the transplant centers may join but "hide" their easier-to-match patients. The proposed research aims to tackle both of these challenges. The goal is to develop algorithms and analysis for exchanges that produce optimal or near-optimal solutions, while providing strong incentive guarantees for transplant centers to join. 2. Dealing with crossmatches: Crossmatch tests require mixing samples of the blood of potential donors and patients, and hence are only done after a matching is computed. Unfortunately, crossmatch tests are quite likely to fail, leading to the collapse of large portions of supposedly optimal exchanges. Optimization that takes crossmatches into account offers significant gains compared to the common practice today. The proposal contains plans to more broadly develop a full theoretical and algorithmic understanding of the integration of crossmatch tests into the optimization, and the fundamental tradeoffs involved.