Intraregional model for end-stage liver disease score variation in liver transplantation: Disparity in our own backyard

Transplant center variability in utilizing nonstandard donors and its impact on the transplantation of patients with lower MELD scores

There is a subset of patients with lower MELD scores who are at substantial risk of waitlist mortality. In order to transplant such patients, transplant centers must utilize "nonstandard" donors (eg, living donors, donation after circulatory death), which are traditionally offered to those patients who are not at the top of the waitlist. We used Organ Procurement and Transplantation data to evaluate center-level and region-level variability in the utilization of nonstandard donors and its impact on MELD at transplant among adult liver-alone non-status 1 patients transplanted from April 1, 2020, to September 30, 2022. The center-level variability in the utilization of nonstandard donors was 4-fold greater than the center-level variability in waitlisting practices (waitlistings with a MELD score of <20). While there was a moderate correlation between center-level waitlisting and transplantation of patients with a MELD score of <20 ( p = 0.58), there was a strong correlation between center-level utilization of nonstandard donors and center-level transplantation of patients with a MELD score of <20 ( p = 0.75). This strong correlation between center-level utilization of "nonstandard" donors and center-level transplantation of patients with a MELD score of <20 was limited to regions 2, 4, 5, 9, and 11. Transplant centers that utilize more nonstandard donors are more likely to successfully transplant patients at lower MELD scores. Public reporting of these data could benefit patients, caregivers, and referring providers, and be used to help maximize organ utilization.

Geographic disparities in access to liver transplantation

Since the Final Rule regarding transplantation was published in 1999, organ distribution policies have been implemented to reduce geographic disparity. While a recent change in liver allocation, termed acuity circles, eliminated the donor service area as a unit of distribution to decrease the geographic disparity of waitlisted patients to liver transplantation, recently published results highlight the complexity of addressing geographic disparity. From geographic variation in donor supply, as well as liver disease burden and differing model for end-stage liver disease (MELD) scores of candidates and MELD scores necessary to receive liver transplantation, to the urban-rural disparity in specialty care access, and to neighborhood deprivation (community measure of socioeconomic status) in liver transplant access, addressing disparities of access will require a multipronged approach at the patient, transplant center, and national level. Herein, we review the current knowledge of these disparities-from variation in larger (regional) to smaller (census tract or zip code) levels to the common etiologies of liver disease, which are particularly affected by these geographic boundaries. The geographic disparity in liver transplant access must balance the limited organ supply with the growing demand. We must identify patient-level factors that contribute to their geographic disparity and incorporate these findings at the transplant center level to develop targeted interventions. We must simultaneously work at the national level to standardize and share patient data (including socioeconomic status and geographic social deprivation indices) to better understand the factors that contribute to the geographic disparity. The complex interplay between organ distribution policy, referral patterns, and variable waitlisting practices with the proportion of high MELD patients and differences in potential donor supply must all be considered to create a national policy strategy to address the inequities in the system.

Expanding Liver Transplant Opportunities in Older Patients With Nonconventional Grafts

INTRODUCTION

Broader use of donation after circulatory death (DCD) and nonconventional grafts for liver transplant helps reduce disparities in organ availability. Limited data, however, exists on outcomes specific to nonconventional graft utilization in older patients. As such, this study aimed to investigate outcomes specific to conventional and nonconventional graft utilization in recipients > 70 y of age.

METHODS

1-to-3 matching based on recipient sex, Model for End-Stage Liver Disease score, and donor type was performed on patients ≥70 and <70 y of age who underwent liver transplant alone at Mayo Clinic Arizona between 2015 and 2020. Primary outcomes were posttransplant patient and liver allograft survival for recipients greater than or less than 70 y of age. Secondary outcomes included grafts utilization patterns, hospital length of stay, need for reoperation, biliary complications and disposition at time of hospital discharge.

RESULTS

In this cohort, 36.1% of grafts came from DCD donors, 17.4% were postcross clamp offers, and 20.8% were nationally allocated. Median recipient ages were 59 and 71 y (P < 0.01). Recipients had similar Intensive care unit (P = 0.82) and hospital (P = 0.14) lengths of stay, and there were no differences in patient (P = 0.68) or graft (P = 0.38) survival. When comparing donation after brain death and DCD grafts in those >70 y, there were no differences in patient (P = 0.89) or graft (P = 0.71) survival.

CONCLUSIONS

Excellent outcomes can be achieved in older recipients, even with use of nonconventional grafts. Expanded use of nonconventional grafts can help facilitate transplant opportunities in older patients.

Center expansion of liver transplants using donation after circulatory death organs is associated with reduced overall waitlist mortality

INTRODUCTION

Waitlist outcomes in liver transplantation (LT) for individual recipients are improved by use of allografts procured through donation after circulatory death (DCD). However, the impact of increased DCD acceptance on overall center outcomes is unknown.

METHODS

Using the United Network for Organ Sharing database, 88 centers performing an average of ≥10 LTs/year between 1/2004 and 12/2019 were compared by percent DCD use quartile and categorized into four phenotypes according to temporal usage trends. Overall center median Model for End-stage Liver Disease at LT (MMaT), waitlist mortality, and waiting time were evaluated.

RESULTS

The overall DCD rate was 6.1% (N = 4906/80,709), ranging from 0% to 25.5%. Centers in the top DCD use quartile had lower MMaT (24 vs. 26; p < .001) and shorter overall waiting times (median 66 days vs. 90 days; p < .001) compared to bottom quartile centers. MMaT increased less over time at centers with increasing DCD use and was lower than at centers with declining DCD use (27 vs. 32; p = .017). Overall waitlist mortality between 2016 and 2019 was lower at increasing DCD use centers (17.8% vs. 22.5%, p = .034), yet did not affect 1-year mortality (p = .747).

CONCLUSIONS

The improved waitlist outcomes at centers with expanded DCD use extend beyond DCD recipients alone without negative consequences to overall post-LT center metrics.

Offer Acceptance Patterns for Liver Donors Aged 70 and Older

Despite a documented survival benefit, older liver donor (OLD, age ≥70) graft offers are frequently declined, with utilization worsening over the last decade. To understand how offer acceptance varies by center, we studied 1113 eventually transplanted OLD grafts from 2009 to 2017 using Scientific Registry of Transplant Recipients (SRTR) data and random-intercept multilevel logistic regression. To understand how center-level acceptance of OLD graft offers might be associated with waitlist and posttransplant outcomes, we studied all adult, actively listed, liver-only candidates and recipients during the study period using Poisson regression (transplant rate), competing risks regression (waitlist mortality), and Cox regression (posttransplant mortality). Among 117 centers, OLD offer acceptance ranged from 0 (23 centers) to 95 acceptances, with a median odds ratio of 2.88. Thus, a candidate may be three times as likely to receive an OLD graft simply by listing at a different center. Centers in the highest quartile (Q4) of OLD acceptance (accepted 39% of OLD offers) accepted more nationally shared organs (Q4 versus Q1: 14.1% versus 0.0%, P < 0.001) and had higher annual liver transplant volume (Q4 versus Q1: 80 versus 21, P < 0.001). After adjustment, nationally shared OLD offers (adjusted odds ratio [aOR]: 0.16, 95% confidence interval [CI]: 0.13-0.20) and offers to centers with higher median Model for End-Stage Liver Disease (MELD) at transplant (aOR: 0.74, 95% CI: 0.62-0.87) were less likely to be accepted. OLD offers to centers with higher annual transplant volume were more likely to be accepted (aOR: 1.21, 95% CI: 1.14-1.30). Additionally, candidates listed at centers within the highest quartile of OLD graft offer acceptance had higher deceased donor liver transplantation (DDLT) rates (adjusted incidence rate ratio: 1.45, 95% CI: 1.41-1.50), lower waitlist mortality (adjusted subhazard ratio: 0.76, 95% CI: 0.72-0.76), and similar posttransplant survival (adjusted hazard ratio: 0.93, 95% CI: 0.86-1.01) when compared with those listed at centers in the lowest quartile of OLD graft offer acceptance. The wide variation in OLD offer acceptance supports the need for optimizing the organ offer process and efficiently directing OLD offers to centers more likely to use them.

Donor Hepatic Occult Collagen Deposition Predisposes to Peritransplant Stress and Impacts Human Liver Transplantation

BACKGROUND AND AIMS

Environmentally triggered chronic liver inflammation can cause collagen deposits, whereas early stages of fibrosis without any specific symptoms could hardly be detectable. We hypothesized that some of the human donor grafts in clinical liver transplantation (LT) might possess unrecognizable fibrosis, affecting their susceptibility to LT-induced stress and hepatocellular damage. This retrospective study aimed to assess the impact of occult hepatic fibrosis on clinical LT outcomes.

APPROACH AND RESULTS

Human (194) donor liver biopsies were stained for collagen with Sirius red, and positive areas (Sirius red-positive area; SRA) were measured. The body mass index, aspartate aminotransferase/alanine aminotransferase ratio, diabetes score was calculated using 962 cases of the donor data at the procurement. LT outcomes, including ischemia-reperfusion injury (IRI), early allograft dysfunction (EAD), and survival rates, were analyzed according to SRA and BARD scores. With the median SRA in 194 grafts of 9.4%, grafts were classified into low-SRA (<15%; n = 140) and high-SRA (≥15%; n = 54) groups. Grafts with high SRA suffered from higher rates of IRI and EAD (P < 0.05) as compared to those with low SRA. Interestingly, high SRA was identified as an independent risk factor for EAD and positively correlated with the donor BARD score. When comparing low-BARD (n = 692) with high-BARD (n = 270) grafts in the same period, those with high BARD showed significantly higher post-LT transaminase levels and higher rates of IRI and EAD.

CONCLUSIONS

These findings from the largest clinical study cohort to date document the essential role of occult collagen deposition in donor livers on LT outcomes. High-SRA and donor BARD scores correlated with an increased incidence of hepatic IRI and EAD in LT recipients. This study provides the rationale for in-depth and prospective assessment of occult fibrosis for refined personalized LT management.

Gender disparities in transplantation

PURPOSE OF REVIEW

Transplantation is the life-saving therapy for patients suffering from end-organ failure, and as such, equitable access to transplantation (ATT) is of paramount importance. Unfortunately, gender/sex-based disparities exist, and despite the transplant community's awareness of this injustice, gender/sex-based disparities have persisted for more than two decades. Importantly, no legislation or allocation policy has addressed inequity in ATT that women disproportionately face. In fact, introduction of the model for end-stage liver disease-based liver allocation system in 2002 widened the gender disparity gap and it continues to be in effect today. Moreover, women suffering from kidney disease are consistently less likely to be referred for transplant evaluation and subsequently less likely to achieve a kidney transplant, yet they comprise the majority of living kidney donors.

RECENT FINDINGS

Acknowledging gender/sex-based disparities in ATT is the first step toward interventions aimed at mitigating this long-standing injustice in healthcare.

SUMMARY

This article provides a background of end-stage liver and kidney disease in women, summarizes the existing literature describing the issue of gender disparity in ATT, and identifies potential areas of intervention and future investigation.

Impact of Model for End-Stage Liver Disease allocation system on outcomes of deceased donor liver transplantation: A single-center experience

Backgrounds/Aims

From June of 2016, the Model for End-Stage Liver Disease (MELD)-based allocation system replaced the Child- Turcotte-Pugh (CTP) score-based system for organ allocation liver in Korea. The aim of this study was to analyze changes in outcomes and arising issues before and after the implementation of the MELD system.

Methods

From June 2014 to June 2018, 129 patients were selected from recipients who underwent deceased donor liver transplantation (DDLT) in Seoul National University Hospital. Pediatric cases were excluded. According to the allocation system, patients were divided into two groups (52 in the MELD group and 77 in the CTP group).

Results

MELD scores of the two groups differed significantly (37.8 ± 2.0 in the MELD group vs. 31.0 ± 8.2 in the CTP group; p = 0.001). The etiology of patients was changed for liver transplantation. The proportion of alcoholic liver cirrhosis increased in the era of the MELD allocation system. However, proportions of hepatitis B related liver cirrhosis and hepatocellular carcinoma were decreased. Six-month mortality rate of the MELD group was 25.0%, which was higher than that (11.7%) of the CTP group (p = 0.022). The 90-day complication rate was significantly higher in the MELD group than in the CTP group (11.5% vs. 2.6%; p = 0.040).

Conclusions

When the MELD allocation system was used to distribute livers to severely ill patients, it resulted in poorer outcomes after surgery and higher proportion of alcoholic cirrhosis. Thus, it is necessary to adjust the MELD allocation system so that outcomes after DDLT could be improved.

Heterogeneous Circles for Liver Allocation

BACKGROUND AND AIMS

In February 2020, the Organ Procurement and Transplantation Network replaced donor service area-based allocation of livers with acuity circles, a system based on three homogeneous circles around each donor hospital. This system has been criticized for neglecting to consider varying population density and proximity to coast and national borders.

APPROACH AND RESULTS

Using Scientific Registry of Transplant Recipients data from July 2013 to June 2017, we designed heterogeneous circles to reduce both circle size and variation in liver supply/demand ratios across transplant centers. We weighted liver demand by Model for End-Stage Liver Disease (MELD)/Pediatric End-Stage Liver Disease (PELD) because higher MELD/PELD candidates are more likely to be transplanted. Transplant centers in the West had the largest circles; transplant centers in the Midwest and South had the smallest circles. Supply/demand ratios ranged from 0.471 to 0.655 livers per MELD-weighted incident candidate. Our heterogeneous circles had lower variation in supply/demand ratios than homogeneous circles of any radius between 150 and 1,000 nautical miles (nm). Homogeneous circles of 500 nm, the largest circle used in the acuity circles allocation system, had a variance in supply/demand ratios 16 times higher than our heterogeneous circles (0.0156 vs. 0.0009) and a range of supply/demand ratios 2.3 times higher than our heterogeneous circles (0.421 vs. 0.184). Our heterogeneous circles had a median (interquartile range) radius of only 326 (275-470) nm but reduced disparities in supply/demand ratios significantly by accounting for population density, national borders, and geographic variation of supply and demand.

CONCLUSIONS

Large homogeneous circles create logistical burdens on transplant centers that do not need them, whereas small homogeneous circles increase geographic disparity. Using carefully designed heterogeneous circles can reduce geographic disparity in liver supply/demand ratios compared with homogeneous circles of radius ranging from 150 to 1,000 nm.

Expanding Role of Donation After Circulatory Death Donors in Liver Transplantation

Better understanding of how to utilize donation after circulatory death (DCD) liver grafts has resulted in improved national outcomes and expansion in the number of DCD liver transplants (LTs). This improvement has been driven by better donor and recipient matching, careful evaluation of hemodynamics during withdrawal of life support, and refinement of the procurement operation. Changes to liver allocation likely will result in increased utilization of DCD liver grafts. Ischemic cholangiopathy remains the Achilles heel of DCD LTs and, although rates have fallen with improved protocols, a certain rate likely is unavoidable. This review discusses contemporary issues with DCD LTs.

Quantifying Sex-Based Disparities in Liver Allocation

Importance

Differences in local organ supply and demand have introduced geographic inequities in the Model for End-stage Liver Disease (MELD) score-based liver allocation system, prompting national debate and patient-initiated lawsuits. No study to our knowledge has quantified the sex disparities in allocation associated with clinical vs geographic characteristics.

Objective

To estimate the proportion of sex disparity in wait list mortality and deceased donor liver transplant (DDLT) associated with clinical and geographic characteristics.

Design, Setting, and Participants

This retrospective cohort study used adult (age ≥18 years) liver-only transplant listings reported to the Organ Procurement and Transplantation Network from June 18, 2013, through March 1, 2018.

Exposure

Liver transplant waiting list.

Main Outcomes and Measures

Primary outcomes included wait list mortality and DDLT. Multivariate Cox proportional hazards regression models were constructed, and inverse odds ratio weighting was used to estimate the proportion of disparity across geographic location, MELD score, and candidate anthropometric and liver measurements.

Results

Among 81 357 adults wait-listed for liver transplant only, 36.1% were women (mean [SD] age, 54.7 [11.3] years; interquartile range, 49.0-63.0 years) and 63.9% were men (mean [SD] age, 55.7 [10.1] years; interquartile range, 51.0-63.0 years). Compared with men, women were 8.6% more likely to die while on the waiting list (adjusted hazard ratio [aHR], 1.11; 95% CI, 1.04-1.18) and were 14.4% less likely to receive a DDLT (aHR, 0.86; 95% CI, 0.84-0.88). In the geographic domain, organ procurement organization was the only variable that was significantly associated with increased disparity between female sex and wait list mortality (22.1% increase; aHR, 1.22; 95% CI, 1.09-1.30); no measure of the geographic domain was associated with DDLT. Laboratory and allocation MELD scores were associated with increases in disparities in wait list mortality: 1.14 (95% CI, 1.09-1.19; 50.1% increase among women) and DDLT: 0.87 (95% CI, 0.86-0.88; 10.3% increase among women). Candidate anthropometric and liver measurements had the strongest association with disparities between men and women in wait list mortality (125.8% increase among women) and DDLT (49.0% increase among women).

Conclusions and Relevance

Our findings suggest that addressing geographic disparities alone may not mitigate sex-based disparities, which were associated with the inability of the MELD score to accurately estimate disease severity in women and to account for candidate anthropometric and liver measurements in this study.

The Changing Landscapes in DCD Liver Transplantation

Purpose of Review

The transplant community continues to look for ways to help address the discordance between donor liver graft availability and patients on the liver transplant waiting list. Donation after circulatory death (DCD) donor livers represents one potential means to help address this discordance. The present review describes the changing landscape of DCD liver transplantation (LT).

Recent Findings

The number of DCD LTs performed annually within the USA has continued to grow on an annual basis. Importantly, national data has demonstrated that outcomes with DCD LT have been improving. This improvement has been driven by better understanding of how to successfully utilize these organs through better donor and recipient matching and careful evaluation of both hemodynamics during withdrawal of life support and the refinement of the procurement operation.

Summary

Despite these improvements in outcome, ischemic cholangiopathy (IC) continues to be the Achilles heel of DCD LT. Emerging technologies such as various forms of machine perfusion may allow for reduction of complications and better prognostication of the risk associated with DCD liver grafts.

Can reporting more lead to less? The role of metrics in assessing liver transplant program performance

Appropriate metrics for performance analysis is an active topic of debate within the transplant community. This study explores current proposals on metric expansion as well as potential metrics and prospective collaborations that have not received widespread discussion within the transplant community. The premature introduction of additional, nonvalidated metrics risks behaviors that may undermine donor utilization and patient access to transplantation.

Moving past "think local, act global": A perspective on geographic disparity

The transplant community has debated the necessity and merits of broader organ distribution for several years, but the debate has been fundamentally shaped by inaccurate assessments of donor supply and demand. The possible legal requirements of distribution must be balanced with (a) the moral and statutory imperatives to reduce inequities resulting from socioeconomic disparity, and (b) the shortcomings of MELD in predicting mortality risk in rural areas. In this viewpoint, we use the example of liver transplantation to discuss the drivers of geographic disparity as a direct consequence of donation rates, local organ use, wealth, and poverty. Seen in this light, strategies seeking to equalize MELD at transplant across the United States risk severely exacerbating existing inequalities in access to health care.

Geographic disparities in liver supply/demand ratio within fixed-distance and fixed-population circles

Recent OPTN proposals to address geographic disparity in liver allocation have involved circular boundaries: the policy selected 12/17 allocated to 150-mile circles in addition to DSAs/regions, and the policy selected 12/18 allocated to 150-mile circles eliminating DSA/region boundaries. However, methods to reduce geographic disparity remain controversial, within the OPTN and the transplant community. To inform ongoing discussions, we studied center-level supply/demand ratios using SRTR data (07/2013-06/2017) for 27 334 transplanted deceased donor livers and 44 652 incident waitlist candidates. Supply was the number of donors from an allocation unit (DSA or circle), allocated proportionally (by waitlist size) to the centers drawing on these donors. We measured geographic disparity as variance in log-transformed supply/demand ratio, comparing allocation based on DSAs, fixed-distance circles (150- or 400-mile radius), and fixed-population (12- or 50-million) circles. The recently proposed 150-mile radius circles (variance = 0.11, P = .9) or 12-million-population circles (variance = 0.08, P = .1) did not reduce the geographic disparity compared to DSA-based allocation (variance = 0.11). However, geographic disparity decreased substantially to 0.02 in both larger fixed-distance (400-mile, P < .001) and larger fixed-population (50-million, P < .001) circles (P = .9 comparing fixed distance and fixed population). For allocation circles to reduce geographic disparities, they must be larger than a 150-mile radius; additionally, fixed-population circles are not superior to fixed-distance circles.

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.

Liver Transplantation Today: Where We Are Now and Where We Are Going

Liver transplantation was made a reality through the bravery, innovation, and persistence of Dr. Thomas Starzl. His death in 2017, at the age of 90, makes us pause to consider how far the field has come since its inception by this remarkable pioneer. It also is an opportunity to evaluate the continued novel innovations which contribute to the growth and potential for liver transplantation in the future. The liver transplant community in 2017 continued to be most significantly challenged by an overwhelming disparity between the need for liver transplant and the shortage of donor organs. The many ways in which this critical shortage are being addressed are examined in this article. The continued debate about equitable and efficacious organ allocation, "the liver wars," has dominated much of the recent past, while efforts to optimize current organ availability have also been aggressively pursued. Efforts to optimize the use of marginal and expanded criteria organs have escalated in recent years and have been accompanied by rigorous scientific evaluation. The ongoing opioid epidemic, combined with the approval and availability of highly effective hepatitis C treatment options, has allowed the increased use of HCV positive organs in HCV positive and negative recipients. Machine perfusion, both cold and warm, has moved solidly into the liver transplant world potentiating optimization of marginal donors and also offering potential modulation of liver grafts (ie, gene therapy, stem cell therapy, and defatting). Finally, pharmacological and mechanical interventions in DCD procurement techniques have contributed to improved outcomes in DCD transplants. All of these are explored in this article as a tribute to innovative spirit of Dr. Starzl and his continued impact on liver transplant today.