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Detalhes

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Publicações

2021

Robust Models for the Kidney Exchange Problem

Autores
Carvalho, M; Klimentova, X; Glorie, K; Viana, A; Constantino, M;

Publicação
INFORMS Journal on Computing

Abstract
Scope and Mission

2021

Fairness models for multi-agent kidney exchange programmes

Autores
Klimentova, X; Viana, A; Pedroso, JP; Santos, N;

Publicação
Omega (United Kingdom)

Abstract
Nowadays there are several countries running independent kidney exchange programmes (KEPs). These programmes allow a patient with kidney failure, having a willing healthy but incompatible donor, to receive a transplant from a similar pair where the donor is compatible with him. Since in general larger patient-donor pools allow for more patients to be matched, this prompts independent programmes (agents) to merge their pools and collaborate in order to increase the overall number of transplants. Such collaboration does however raise a problem: how to assign transplants to agents so that there is a balance between the contribution each agent brings to the merged pool and the benefit it gets from the collaboration. In this paper we propose a new Integer Programming model for multi-agent kidney exchange programmes (mKEPs). It considers the possible existence of multiple optimal solutions in each matching period of a KEP and, in consecutive matching periods, selects the optimal solution among the set of alternative ones in such a way that in the long-term the benefit each agent gets from participating in the mKEP is balanced accordingly to a given criterion. This is done by use of a memory mechanism. Extensive computational tests show the benefit of mKEPs, when compared to independent KEPs, in terms of potential increase in the number of transplants. Furthermore, they show that, under different policies, the number of additional transplants each agent receives can vary significantly. More importantly, results show that the proposed methodology consistently obtains more stable results than methodologies that do not use memory. © 2020 Elsevier Ltd

2021

Modelling and optimisation in European Kidney Exchange Programmes

Autores
Biro, P; van de Klundert, J; Manlove, D; Pettersson, W; Andersson, T; Burnapp, L; Chromy, P; Delgado, P; Dworczak, P; Haase, B; Hemke, A; Johnson, R; Klimentova, X; Kuypers, D; Costa, AN; Smeulders, B; Spieksma, F; Valentin, MO; Viana, A;

Publicação
European Journal of Operational Research

Abstract
The complex multi-criteria optimisation problems arising in Kidney Exchange Programmes have received considerable attention both in practice and in the scientific literature. Whereas theoretical advancements are well reviewed and synthesised, this is not the case for practice. We present a synthesis of models and methods applied in present European Kidney Exchange Programmes, which is based on detailed descriptions we created for this purpose. Most descriptions address national programmes, yet we also present findings on emerging cross-national programmes. The synthesis provides a systematic and detailed description of the models and methods the programmes use, revealing important commonalities as well as considerable variation among them. Rather than distilling a single best practice from these results, we find that the variation in models and methods arises because of variation in country characteristics, policies, and ethics. The synthesised state of the art may benefit future national and cross-national initiatives and direct future theoretical contributions within and across the boundaries of the Operations Research discipline. © 2019

2020

Compensation Scheme With Shapley Value For Multi-Country Kidney Exchange Programmes

Autores
Biro, P; Gyetvai, M; Klimentova, X; Pedroso, JP; Pettersson, W; Viana, A;

Publicação
ECMS 2020 Proceedings edited by Mike Steglich, Christian Mueller, Gaby Neumann, Mathias Walther

Abstract

2019

Maximizing the expected number of transplants in kidney exchange programs with branch-and-price

Autores
Alvelos, F; Klimentova, X; Viana, A;

Publicação
Annals of Operations Research

Abstract
In this paper, we propose a branch-and-price approach for solving the problem of maximizing the expected number of transplants in Kidney Exchange Programs (KEPs). In these programs, the decision on which transplants will be conducted is usually made with the support of optimization models with the assumption that all operations will take place. However, after a plan of transplants is defined, a pair may leave the KEP or a more accurate compatibility evaluation exam may invalidate a transplant. To model these possible events we consider probabilities of failure of vertices and of arcs and the objective of maximizing the expected number of transplants. The proposed approach is based on the so-called cycle formulation, where decision variables are associated with cycles. Built on the concept of type of cycle a branch-and-price algorithm is conceived. One subproblem is defined for each type of cycle. We present computational results of the proposed branch-and-price algorithm and compare them with solving directly the cycle formulation (with a general purpose mixed integer programming solver—CPLEX) showing that the proposed approach is the only one suitable for larger instances. © 2017 Springer Science+Business Media, LLC