Kidney Exchange

Most transplanted kidneys are from cadavers, but there are also substantial numbers of transplants from live donors. Recently, there have started to be kidney exchanges involving two donor-patient pairs such that each donor cannot give a kidney to the intended recipient because of immunological incompatibility, but each patient can receive a kidney from the other donor. Exchanges are also made in which a donor-patient pair makes a donation to someone on the queue for a cadaver kidney, in return for the patient in the pair receiving the highest priority for a compatible cadaver kidney when one becomes available. We explore how such exchanges can be arranged efficiently and incentive compatibly. The problem resembles some of the housing' problems studied in the mechanism design literature for indivisible goods, with the novel feature that while live donor kidneys can be assigned simultaneously, the cadaver kidneys must be transplanted immediately upon becoming available. In addition to studying the theoretical properties of the design we propose for a kidney exchange, we present simulation results suggesting that the welfare gains would be substantial, both in increased number of feasible live donation transplants, and in improved match quality of transplanted kidneys.

Kidney Exchange

Most transplanted kidneys are from cadavers, but there are also substantial numbers of transplants from live donors. Recently, there have started to be kidney exchanges involving two donor-patient pairs such that each donor cannot give a kidney to the intended recipient because of immunological incompatibility, but each patient can receive a kidney from the other donor. Exchanges are also made in which a donor- patient pair makes a donation to someone on the queue for a cadaver kidney, in return for the patient in the pair receiving the highest priority for a compatible cadaver kidney when one becomes available. We explore how such exchanges can be arranged efficiently and incentive compatibly. The problem resembles some of the "housing" problems studied in the mechanism design literature for indivisible goods, with the novel feature that while live donor kidneys can be assigned simultaneously, the cadaver kidneys must be transplanted immediately upon becoming available. In addition to studying the theoretical properties of the design we propose for a kidney exchange, we present simulation results suggesting that the welfare gains would be substantial, both in increased number of feasible live donation transplants, and in improved match quality of transplanted kidneys.

Maximum weight cycle packing in directed graphs, with application to kidney exchange programs

Centralized matching programs have been established in several countries to organize kidney exchanges between incompatible patient-donor pairs. At the heart of these programs are algorithms to solve kidney exchange problems, which can be modelled as cycle packing problems in a directed graph, involving cycles of length 2, 3, or even longer. Usually, the goal is to maximize the number of transplants, but sometimes the total benefit is maximized by considering the differences between suitable kidneys. These problems correspond to computing cycle packings of maximum size or maximum weight in directed graphs. Here we prove the APX-completeness of the problem of finding a maximum size exchange involving only 2-cycles and 3-cycles. We also present an approximation algorithm and an exact algorithm for the problem of finding a maximum weight exchange involving cycles of bounded length. The exact algorithm has been used to provide optimal solutions to real kidney exchange problems arising from the National Matching Scheme for Paired Donation run by NHS Blood and Transplant, and we describe practical experience based on this collaboration

Paired and altruistic kidney donation in the UK: Algorithms and experimentation

We study the computational problem of identifying optimal sets of kidney exchanges in the UK. We show how to expand an integer programming-based formulation due to Roth et al. [2007] in order to model the criteria that constitute the UK definition of optimality. The software arising from this work has been used by the National Health Service Blood and Transplant to find optimal sets of kidney exchanges for their National Living Donor Kidney Sharing Schemes since July 2008. We report on the characteristics of the solutions that have been obtained in matching runs of the scheme since this time. We then present empirical results arising from experiments on the real datasets that stem from these matching runs, with the aim of establishing the extent to which the particular optimality criteria that are present in the UK influence the structure of the solutions that are ultimately computed. A key observation is that allowing four-way exchanges would be likely to lead to a moderate number of additional transplants

Aerospace Medicine and Biology: A continuing bibliography with indexes, supplement 192

This bibliography lists 247 reports, articles, and other documents introduced into the NASA scientific and technical information system in March 1979

Patient-level simulation of alternative deceased donor kidney allocation schemes for patients awaiting transplantation in the United Kingdom

In the United Kingdom, the number of patients waiting to receive a kidney transplant far outstrips the supply of donor organs, thereby making some form of rationing inevitable. The criteria for rationing can be made explicit in the design of a kidney allocation scheme, which typically aims to achieve a balance between efficiency, defined as maximising health benefits from a limited resource, and equity in the distribution of that resource. In the past, kidney allocation schemes have focussed on waiting time as one of the criteria to promote equity in access to transplantation. Over time, increasing emphasis has been placed on closer tissue matching between recipients and donors after this was shown to result in better post-transplant outcomes. More recently, there has been recognition of variability in the quality of donor kidneys such that not all donor kidneys will result in equally good survival outcomes and not all patients will derive the same benefit from a given donor kidney. This thesis describes the development of a patient-level simulation model that compares five different approaches to allocating kidneys from across the equity-efficiency spectrum. Emphasis is placed on characterising heterogeneity in the data inputs that are used to inform the simulation. This is achieved by using various regression modelling strategies to analyse patient-level data to facilitate prediction of costs, health-state utilities and survival conditional on covariates such as age, comorbidities and treatment modality. For each allocation scheme, the simulation model reports total costs, life years and quality-adjusted life years across the patient population. The simulation model can be used to quantify not only the magnitude of health gains associated with moving from one kidney allocation approach to another, but also the impact in terms of equity in access to transplantation and the distribution of outcomes across different patient groups. The outputs of the simulation can be used to inform discussions about equity-efficiency tradeoffs in the design of a kidney allocation policy

Dynamic Decision Models for Managing the Major Complications of Diabetes

Diabetes is the sixth-leading cause of death and a major cause of cardiovascular and renal diseases in the U.S. In this dissertation, we consider the major complications of diabetes and develop dynamic decision models for two important timing problems: Transplantation in prearranged paired kidney exchanges (PKEs) and statin initiation. Transplantation is the most viable renal replacement therapy for end-stage renal disease (ESRD) patients, but there is a severe disparity between the demand and supply of kidneys for transplantation. PKE, a cross-exchange of kidneys between incompatible patient-donor pairs, overcomes many difficulties in matching patients with incompatible donors. In a typical PKE, transplantation surgeries take place simultaneously so that no donor may renege after her intended recipient receives the kidney. We consider two autonomous patients with probabilistically evolving health statuses in a PKE, and model their transplant timing decisions as a discrete-time non-zero-sum stochastic game. We explore necessary and sufficient conditions for patients' decisions to form a stationary-perfect equilibrium, and formulate a mixed-integer linear programming (MIP) representation of equilibrium constraints to characterize a socially optimal stationary-perfect equilibrium. We calibrate our model using large scale clinical data. We quantify the social welfare loss due to patient autonomy and demonstrate that the objective of maximizing the number of transplants may be undesirable. Patients with Type 2 diabetes have higher risk of heart attack and stroke, and if not treated these risks are confounded by lipid abnormalities. Statins can be used to treat such abnormalities, but their use may lead to adverse outcomes. We consider the question of when to initiate statin therapy for patients with Type 2 diabetes. We formulate a Markov decision process (MDP) to maximize the patient's quality-adjusted life years (QALYs) prior to the first heart attack or stroke. We derive sufficient conditions for the optimality of control-limit policies with respect to patient's lipid-ratio (LR) levels and age and parameterize our model using clinical data. We compute the optimal treatment policies and illustrate the importance of individualized treatment factors by comparing their performance to those of the guidelines in use in the U.S

Preserving organ function of marginal donor kidneys

Niertransplantatie is de beste medische behandeling voor patiënten die lijden aan eindstadium nierfalen. De afgelopen decennia is de samenstelling van de overleden donorpool radicaal veranderd, zodanig dat er steeds meer organen beschikbaar komen van oudere donoren, die vaak al meerdere aandoeningen in de voorgeschiedenis hebben, of van zogenaamde non-heart beating donoren bij wie de orgaanuitname pas kan beginnen wanneer het hart al enkele minuten stil heeft gestaan. Zulke orgaandonoren worden ook wel marginale donoren genoemd. Dit proefschrift beschrijft de resultaten van klinische en pre-klinische studies op het gebied van niertransplantatie. In deze studies wordt de invloed die verscheidene karakteristieken van overleden orgaandonoren op het transplantatieresultaat hebben gekwantificeerd. Tevens wordt het effect onderzocht van interventies vóór of gedurende orgaanpreservatie, die zijn gericht op het beter conserveren van de orgaankwaliteit voorafgaand aan de transplantatie. Daarnaast beschrijft het proefschrift een studie waarin biomarkers worden gemeten in de orgaanpreservatievloeistof en een andere studie waarin de vasculaire weerstand wordt bepaald tijdens machinale preservatie van donornieren. Deze beide studies hebben als doel het voorspellen van de vitaliteit en de functie van het orgaan na transplantatie. Hoewel de resultaten van de studies in dit proefschift betrekking hebben op nieren afkomstig van alle typen overleden donoren, zijn ze het meest relevant voor marginale donornieren. Aangezien de functie en levensduur van zulke nieren na transplantatie vaak suboptimaal zijn, is extra informatie over hun kwaliteit nog vóór transplantatie belangrijk. Tevens zijn nieuwe interventies die de orgaanfunctie ná transplantatie verbeteren noodzakelijk