Liver sharing and organ procurement organization performance under redistricted allocation

Allocating kidneys in optimized heterogeneous circles

Recently, the Organ Procurement and Transplant Network approved a plan to allocate kidneys within 250-nm circles around donor hospitals. These homogeneous circles might not substantially reduce geographic differences in transplant rates because deceased donor kidney supply and demand differ across the country. Using Scientific Registry of Transplant Recipients data from 2016-2019, we used an integer program to design unique, heterogeneous circles with sizes between 100 and 500 nm that reduced supply/demand ratio variation across transplant centers. We weighted demand according to wait time because candidates who have waited longer have higher priority. We compared supply/demand ratios and average travel distance of kidneys, using heterogeneous circles and 250 and 500-nm fixed-distance homogeneous circles. We found that 40% of circles could be 250 nm or smaller, while reducing supply/demand ratio variation more than homogeneous circles. Supply/demand ratios across centers for heterogeneous circles ranged from 0.06 to 0.13 kidneys per wait-year, compared to 0.04 to 0.47 and 0.05 to 0.15 kidneys per wait-year for 250-nm and 500-nm homogeneous circles, respectively. The average travel distance for kidneys using heterogeneous, and 250-nm and 500-nm fixed-distance circles was 173 nm, 134 nm, and 269 nm, respectively. Heterogeneous circles reduce geographic disparity compared to homogeneous circles, while maintaining reasonable travel distances.

Ensuring the need is met: A 50-year simulation study of the National Kidney Registry's family voucher program

The National Kidney Registry (NKR) Advanced Donation Program enables living donors the opportunity to donate altruistically, or in advance of a potential recipient's transplant, and to receive a voucher that can be redeemed for a future transplant facilitated by the NKR. Family vouchers allow a donor to identify multiple individuals within their immediate family, with the first person in that group in need of a transplant being prioritized to receive a kidney. An increase in vouchers introduces concerns that demand for future voucher redemptions could exceed the supply of available donors and kidneys. A Monte Carlo simulation model was constructed to estimate the annual number of voucher redemptions relative to the number of kidneys available over a 50-year time horizon under several projected scenarios for growth of the program. In all simulated scenarios, the number of available kidneys exceeded voucher redemptions every year. While not able to account for all real-life scenarios, this simulation study found that the NKR should be able to satisfy the likely redemption of increasing numbers of vouchers under a range of possible scenarios over a 50-year time horizon. This modeling exercise suggests that a donor family's future needs can be satisfied through the voucher program.

Addressing Critiques of the Proposed CMS Metric of Organ Procurement Organ Performance: More Data Isn't Better

BACKGROUND

Centers for Medicare and Medicaid Services (CMS) has proposed a rule change to redefine the metric by which organ procurement organizations (OPOs) are evaluated. The metric relies on Centers for Disease Control and Prevention (CDC) data on inpatient deaths from causes consistent with donation among patients <75 years of age. Concerns have been raised that this metric does not account for rates of ventilation, and prevalence of cancer and severe sepsis, without objective data to substantiate or refute such concerns.

METHODS

We estimated OPO-level donation rates using CDC data, and used Agency for Healthcare Research and Quality/Healthcare Cost and Utilization Project data from 43 State Inpatient Databases to calculate "adjusted" donation rates.

RESULTS

The CMS metric and the ventilation-adjusted CMS metric were highly concordant in absolute terms (Spearman and Pearson correlation coefficients ≥0.95). In the Bland-Altman plot, 100% (48/48) of paired values (standard deviations [SDs] of the CMS and "ventilation adjusted" metrics) were within 1.96 SDs of the mean difference, with near-perfect correlation in Passing and Bablok regression (Lin's concordance correlation coefficient: 0.97). The CMS metric and the ventilation/cancer/sepsis-adjusted metric were highly concordant in absolute terms (Spearman and Pearson correlation coefficients ≥0.94). In the Bland-Altman plot, 97.9% (47/48) of paired values (SDs of the CMS and "ventilation/cancer/sepsis adjusted" metrics) were within 1.96 SDs of the mean difference, with near-perfect correlation in the Passing and Bablok regression (Lin's concordance correlation coefficient: 0.97).

CONCLUSIONS

These conclusions should provide CMS, and the transplant community, with comfort that the proposed CMS metric using CDC inpatient death data as a tool to compare OPO is not compromised by its lack of inclusion of ventilation or other comorbidity data.

Importance of incorporating standardized, verifiable, objective metrics of organ procurement organization performance into discussions about organ allocation

Identifying and supporting specific organ procurement organizations (OPOs) with the greatest opportunity to increase donation rates could significantly increase the number of organs available for transplant. Accomplishing this is complicated by current Scientific Registry of Transplant Recipients/Centers for Medicare & Medicaid Services metrics of donation rates and OPO performance that rely on eligible deaths. These data are self-reported and unverifiable and have been shown to underestimate potential organ donors. We examine the limitations of current OPO performance/donation metrics to inform discussions related to strategies to increase donation. We propose changing to a simple, verifiable, and uniformly applied donation metric. This would allow the transplant community to (1) better understand inherent differences in donor availability based on geography and (2) identify underperforming areas that would benefit from systems improvement agreements to increase donation rates.

State-Based Liver Distribution: Broad Sharing With Less Harm to Vulnerable and Underserved Communities Compared With Concentric Circles

Allocation of livers for transplantation faces regulatory pressure to move toward broader sharing. A current proposal supported by the United Network for Organ Sharing Board of Directors relies on concentric circles, but its effect on socioeconomic inequities in access to transplant services is poorly understood. In this article, we offer a proposal that uses the state of donation as a unit of distribution, given that the state is a recognized unit of legal jurisdiction and socioeconomic health in many contexts. The Scientific Registry of Transplant Recipients liver simulated allocation model algorithm was used to generate comparative estimates of regional transplant volume and the impact of these considered changes with regard to vulnerable and high-risk patients on the waiting list and to disparities in wait-list access. State-based liver distribution outperforms the concentric circle models in overall system efficiency, reduced discards, and minimized flights for organs. Furthermore, the efflux of organs from areas of greater sociodemographic vulnerability and lesser wait-list access is more than 2-fold lower in a state-based model than in concentric circle alternatives. In summary, we propose that a state-based system offers a legally defensible, practical, and ethically sound alternative to geometric zones of organ distribution.

New paradigms for organ allocation and distribution in liver transplantation

PURPOSE OF REVIEW

The 'Final Rule,' issued by the Health Resources and Service Administration in 2000, mandated that liver allocation policy should be based on disease severity and probability of death, and - among other factors - should be independent of a candidate's residence or listing. As a result, the Organ Procurement Transplantation Network/United Network for Organ Sharing (UNOS) has explored policy changes addressing geographic disparities without compromising outcomes.

RECENT FINDINGS

Major paradigm shifts are underway in U.S. liver allocation policy. New hepatocellular carcinoma exception policy incorporates tumor characteristics associated with posttransplantation outcomes, whereas a National Liver Review Board will promote a standardized process for awarding exception points. Meanwhile, following extensive debate, new allocation policy aims to reduce geographic disparity by broadening sharing to the UNOS region and 150-mile circle around the donor hospital for liver transplant candidates with a calculated model for end-stage liver disease score at least 32. Unnecessary organ travel will be reduced by granting 3 'proximity points' to candidates within the same donation service area (DSA) as a liver donor or within 150 nautical miles of the donor hospital, regardless of DSA or UNOS region.

SUMMARY

This review provides an evaluation of major policy changes in liver allocation from 2016 to 2018.

Geographic variation in liver transplantation persists despite implementation of Share35

AIM

Geographic disparities persist in the USA despite locoregional organ sharing policies. The impact of national organ sharing policies on waiting-list mortality on a regional basis remains unknown.

METHODS

Data on all adult liver transplants between 1 February 2002 and 31 March 2015 were obtained from the United Network for Organ Sharing/Organ and Transplantation Network. Multivariable Cox proportional hazards models were constructed in a time-to-event analysis to estimate waiting-list mortality for the pre- and post-Share35 eras.

RESULTS

In the analyzed time period, 134 247 patients were listed for transplantation and 54 510 received organs (42.8%). Listing volume increased following the introduction of the Share35 organ sharing policy (15 976 candidates pre- vs. 18 375 post) without significant regional changes as did the number of transplants (7210 pre- vs. 8224 post). Waiting-list mortality improved from 12.2% to 8.1% (P < 0.001). Adjusted waiting-list mortality ratios remained geographically disparate. Region 10 and region 11 had lower hazard ratios (HR) but still had increased mortality (1.46, 95% confidence interval [CI] 1.34-1.60, P < 0.001; and HR 1.49, 95% CI 1.37-1.62, P < 0.001, respectively). Regions 3 and 6 had increased HR with persistently elevated waiting-list mortality (1.79, 95% CI 1.66-1.93, P < 0.001; and HR 1.29, 95% CI 1.16-1.45, P < 0.001, respectively). Model for End-state Liver Disease (MELD) exception continued to propagate a survival benefit (HR 0.65, 95% CI 0.63-0.68, P < 0.001).

CONCLUSIONS

Although overall waiting-list mortality has decreased, geographic disparities persist, but appear reduced despite broader sharing policies enacted by Share35. The advantage afforded by MELD exception, while still present, was diminished by Share35 as organs are being shifted to MELD >35 candidates. The disparities highlighted by our findings imply a need to review current allocation policies to best balance local, regional, and national transplant environments.

Outcomes and disparities in liver transplantation will be improved by redistricting-cons

PURPOSE OF REVIEW

Over the last 2 years, the liver transplant community has been debating a proposal to redraw the maps of organ distribution. The basis for these proposed changes is reported disparities in severity of illness at transplantation across the USA - however, this is based on the allocation model for end-stage liver disease score. In this review, we provide a critical overview of the redistribution proposal, its flaws and how it may worsen outcomes and exacerbate disparities in liver transplantation.

RECENT FINDINGS

The main findings we highlight are data questioning the disparity metric used to justify the redistribution. We also review data published in recent articles and presented at public forums questioning whether there truly are disparities in access to transplant care among the broader population with liver disease, and whether disparities even getting to the waitlist are important and not to be ignored.

SUMMARY

This review article highlights major methodological and policy flaws with the current redistribution proposal. We demonstrate how the waitlist disparities that the proposal is intended to fix are not as they seem. Furthermore, if this proposal is passed, outcomes of liver transplantation nationally may worsen, and disparities for those with limited access to healthcare will worsen.

Adult Liver Allocation in Eurotransplant

Liver allocation in Eurotransplant is complex because allocation rules need to follow not only the guidelines of the European Commission but also the specific regulations of each of the 7 Eurotransplant countries with active liver transplant programs. Thirty-eight liver transplant centers served a population of about 135 million in 2015. Around 1600 deceased donor livers are transplanted annually. The number of deceased organ donors remains stable but donor age is increasing. Nevertheless, liver utilization rates are unchanged at around 80%. Donation after circulatory determination of death (DCD) increased fourfold in the past decade. In Belgium and the Netherlands, DCDs were responsible for 30% of deceased donor liver transplant activity in 2015; Austria only occasionally transplants a DCD liver; other Eurotransplant countries do not have active DCD programs. The most frequent indications for liver transplantation are alcoholic liver disease, hepatocellular carcinoma, and viral hepatitis. Livers are allocated first internationally to high urgency status patients or those with an approved combined organ status (for a liver in combination with heart, lung, intestine, or pancreas) and then on a national basis where allocation is recipient-driven or center-driven, depending on country-specific rules. Median waiting time for an elective liver transplant was 4,4 months in 2015; high urgency status patients waited a median of 2 days for a suitable liver. Mortality on the waiting list was 18% in 2015, 4% of patients were delisted because they became unfit for transplantation. One-year and 5-year risk unadjusted adult patient survival after transplantation is 80% and 65%, respectively.

A Concentric Neighborhood Solution to Disparity in Liver Access That Contains Current UNOS Districts

BACKGROUND

Policymakers are deliberating reforms to reduce geographic disparity in liver allocation. Public comments and the United Network for Organ Sharing Liver and Intestinal Committee have expressed interest in refining the neighborhoods approach. Share 35 and Share 15 policies affect geographic disparity.

METHODS

We construct concentric neighborhoods superimposing the current 11 regions. Using concepts from concentric circles, we construct neighborhoods for each donor service area (DSA) that consider all DSAs within 400, 500, or 600 miles as neighbors. We consider limiting each neighborhood to 10 DSAs and use no metrics for liver supplies and demands. We change Model for End-Stage Liver Disease (MELD) thresholds for the Share 15 policy to 18 or 20 and apply 3- and 5-point MELD proximity boosts to enhance local priority, control travel distances, and reduce disparity. We conduct simulations comparing current allocation with the neighborhoods and sharing policies.

RESULTS

Concentric neighborhoods structures provide an array of solutions where simulation results indicate that they reduce geographic disparity, annual mortalities, and the airplane travel distances by varying degrees. Tuning of the parameters and policy combinations can lead to beneficial improvements with acceptable transplant volume loss and reductions in geographic disparity and travel distance. Particularly, the 10-DSA, 500-mile neighborhood solution with Share 35, Share 15, and 0-point MELD boost achieves such while limiting transplant volume losses to below 10%.

CONCLUSIONS

The current 11 districts can be adapted systematically by adding neighboring DSAs to improve geographic disparity, mortality, and airplane travel distance. Modifications to Share 35 and Share 15 policies result in further improvements. The solutions may be refined further for implementation.

Sent Liver Grafts Do Not Have a Detrimental Impact on Post-transplant Outcome

INTRODUCTION

"Sent livers" (SL) (interregional allocated organs) are considered extended donor criteria grafts. These grafts influence post-transplant outcome. In our donor allocation program, the number of allocated SLs is increasing. The aim of our study is to provide data supporting the possibility to enlarge the use of SLs through adequate donor-to-recipient matching.

METHODS

A retrospective analysis was carried out from our prospective-collected database during 2014.

RESULTS

Fifty-seven liver transplantations (LTs) were included: 22 SLs and 35 grafts procured by us (nSLs). Only donor risk index among donor characteristics showed a trend toward significant values (SL 1.901 vs nSL 1.726, P = .07). Among LT variables, the number of patients who received interleukin-2 inhibitor induction (SL 7 vs nSL 20, P < .05) and the presence of hepatocellular carcinoma (SL 50% vs nSL 34%, P < .05) reached statistical significance. One case of primary nonfunction occurred in the nSL group. No major retrieval injuries were observed. Retransplantation was performed in 6 cases (2 SLs and 4 nSLs). One patient in the SL group died after retransplantation. Graft survival rates at 1, 3, 6, and 12 months were 100%, 100%, 90%, 86% and 91%, 86%, 86%, 86% (P = .79) in SL and nSL groups, respectively.

DISCUSSION

SL performance did not differ from that of nSL. SLs were usually allocated to noncritical candidates, and nSLs were transplanted more frequently in decompensated recipients. Despite this peculiar donor-recipient match, grafts survival was similar in the 2 groups of patients.

Current Issues in Liver Transplantation

The state of liver transplantation continues to evolve. This article focuses on 3 separate yet important issues within this field. First, there is a proposal to change the allocation of donor livers in the United States. The fundamental premise of this proposal is to equalize access to donor livers across the country. To accomplish this goal, the proposal is to increase the geographic area of liver allocation. As might be expected, there is a great deal of controversy surrounding the possibility of a major change in liver allocation and distribution. A second area of interest, and perhaps the most important therapeutic breakthrough in the field of hepatology, is the introduction of direct-acting antiviral agents against hepatitis C virus (HCV) infection. With cure rates up to 100%, an increasing proportion of liver transplant candidates and recipients are being cured of HCV infection with therapies that have minimal side effects. Consequently, the impact of HCV infection on patient and graft survival will likely improve substantially over the next few years. Finally, this article reviews the role of donor-specific antibodies (DSAs) in antibody-mediated rejection. Long recognized as an important factor in graft survival in renal transplantation, DSAs have recently been shown to be a strong predictor of graft and patient survival in liver transplantation. However, the importance of DSAs in liver transplantation is uncertain, in large part due to the absence of proven therapies.