Persistent sex disparity in liver transplantation rates

Sex and Size Disparities in Access to Liver Transplant for Patients With Hepatocellular Carcinoma

Importance

Women on the liver transplant waiting list are less likely to undergo a transplant than men. Recent approaches to resolving this disparity have involved adjustments to Model for End-Stage Liver Disease (MELD) scoring, but this will not affect candidates who rely on exception scores rather than calculated MELD score, the majority of whom have hepatocellular carcinoma (HCC).

Objective

To evaluate the association between female sex, candidate size, and access to liver transplant among wait-listed patients with HCC.

Design, Setting, and Participants

This retrospective cohort study used US transplant registry data of all adult (aged ≥18 years) wait-listed liver transplant candidates receiving an HCC exception score between January 1, 2010, and March 2, 2023.

Exposure

Wait-listed liver transplant candidate sex.

Main Outcomes and Measures

The association of female sex with (1) deceased-donor liver transplant (DDLT) and (2) death or waiting list removal for health deterioration were estimated using multivariable competing-risks regression. Results with and without adjustment for candidate height and weight (mediators of the sex disparity) were compared.

Results

The cohort included 31 725 candidates with HCC (mean [SD] age at receipt of exception, 61.2 [7.1] years; 76.3% men). Compared with men, women had a lower 1-year cumulative incidence of DDLT (50.8% vs 54.0%; P < .001) and a higher 1-year cumulative incidence of death or delisting for health deterioration (16.2% vs 15.0%; P = .002). After adjustment, without accounting for size, women had a lower incidence of DDLT (subdistribution hazard ratio [SHR], 0.92; 95% CI, 0.89-0.95) and higher incidence of death or delisting (SHR, 1.06; 95% CI, 1.00-1.13) compared with men. When adjusting for candidate height and weight, there was no association of female sex with incidence of DDLT or death or delisting. However, at a height cutoff of 166 cm, short women compared with short men were still less likely to undergo a transplant (SHR, 0.93; 95% CI, 0.88-0.99).

Conclusions and Relevance

In this study, women with HCC were less likely to receive a DDLT and more likely to die while wait-listed than men with HCC; these differences were largely (but not entirely) explained by sex-based differences in candidate size. For candidates listed with exception scores, additional changes to allocation policy are needed to resolve the sex disparity, including solutions to improve access to size-matched donor livers for smaller candidates.

Evaluating the Correlation Between Anteroposterior Diameter, Body Surface Area, and Height for Liver Transplant Donors and Recipients

Background

Small stature and female sex correlate to decreased deceased donor liver transplant (DDLT) access and higher waitlist mortality. However, efforts are being made to improve access and equity of allocation under the new continuous distribution (CD) system. Liver anteroposterior diameter (APD) is a method used by many centers to determine size compatibility for DDLT but is not recorded systematically, so it cannot be used for allocation algorithms. We therefore seek to correlate body surface area (BSA) and height to APD in donors and recipients and compare waitlist outcomes by these factors to support their use in the CD system.

Methods

APD was measured from single-center DDLT recipients and donors with cross-sectional imaging. Linear, Pearson, and PhiK correlation coefficient were used to correlate BSA and height to APD. Competing risk analysis of waitlist outcomes was performed using United Network for Organ Sharing data.

Results

For 143 pairs, donor BSA correlated better with APD than height (PhiK = 0.63 versus 0.20). For recipient all comers, neither BSA nor height were good correlates of APD, except in recipients without ascites, where BSA correlated well (PhiK = 0.63) but height did not. However, among female recipients, BSA, but not height, strongly correlated to APD regardless of ascites status (PhiK = 0.80 without, PhiK = 0.70 with). Among male recipients, BSA correlated to APD only in those without ascites (PhiK = 0.74). In multivariable models, both BSA and height were predictive of waitlist outcomes, with higher values being associated with increased access, decreased delisting for death/clinical deterioration, and decreased living donor transplant (model concordance 0.748 and 0.747, respectively).

Conclusions

Taken together, BSA is a good surrogate for APD and can therefore be used in allocation decision making in the upcoming CD era to offset size and gender-based disparities among certain candidate populations.

Affordable Care Act Medicaid expansion associated with increased liver transplant waitlist access without worsening mortality

It is unclear what impact Affordable Care Act (ACA) Medicaid expansion has had on the liver transplantation (LT) waitlist. We aimed to assess associations between ACA Medicaid expansion and LT waitlist outcomes. The United Network for Organ Sharing Standard Transplant Analysis and Research (UNOS STAR) database was queried for patients listed for LT between January 1, 2009, and December 31, 2018. Our primary outcome was waitlist mortality and our secondary outcomes included Medicaid use on the LT waitlist and transplant rate. States were divided into groups based on their expansion status and the study period was divided into 2 time intervals-pre-expansion and post-expansion. Difference-in-difference (DiD) models were created to assess the impacts of expansion on each of the outcomes and for racial/ethnic and sex groups. In total, 56,414 patients from expansion states and 32,447 patients from nonexpansion states were included. Three-year waitlist mortality decreased at a similar rate in both cohorts [DiD estimate: 0.1, (95% CI, -1.1, -1.4), p = 0.838], but Medicaid use increased [DiD estimate: +7.7, (95% CI, 6.7, 8.7), p < 0.001] to a greater degree in expansion states after expansion than nonexpansion states. Between the 2 time intervals, Medicaid use on the LT waitlist increased from 19.4% to 26.1% in expansion states but decreased from 13.4% to 12.1% in nonexpansion states. In patients on Medicaid, there was a slight increase in the 3-year transplant rate associated with Medicaid expansion [DiD estimate +5.0, (95% CI, 1.8, 8.3), p = 0.002], which may in part be explained by differences in patient characteristics. Medicaid expansion was associated with increased Medicaid use on the LT waitlist without worsening overall waitlist mortality or transplant rate, suggesting that lenient and widespread public health insurance may increase access to the LT waitlist without adversely affecting outcomes.

Sex-based Disparities in Access to Liver Transplantation for Waitlisted Patients With Model for End-stage Liver Disease Score of 40

OBJECTIVE

To determine the association of sex with access to liver transplantation among candidates with the highest possible model for end-stage liver disease score (MELD 40).

BACKGROUND

Women with end-stage liver disease are less likely than men to receive liver transplantation due in part to MELD's underestimation of renal dysfunction in women. The extent of the sex-based disparity among patients with high disease severity and equally high MELD scores is unclear.

METHODS

Using national transplant registry data, we compared liver offer acceptance (offers received at match MELD 40) and waitlist outcomes (transplant vs death/delisting) by sex for 7654 waitlisted liver transplant candidates from 2009 to 2019 who reached MELD 40. Multivariable logistic and competing-risks regression was used to estimate the association of sex with the outcome and adjust for the candidate and donor factors.

RESULTS

Women (N = 3019, 39.4%) spent equal time active at MELD 40 (median: 5 vs 5 days, P = 0.28) but had lower offer acceptance (9.2% vs 11.0%, P < 0.01) compared with men (N = 4635, 60.6%). Adjusting for candidate/donor factors, offers to women were less likely accepted (odds ratio = 0.87, P < 0.01). Adjusting for candidate factors, once they reached MELD 40, women were less likely to be transplanted (subdistribution hazard ratio = 0.90, P < 0.01) and more likely to die or be delisted (subdistribution hazard ratio = 1.14, P = 0.02).

CONCLUSIONS

Even among candidates with high disease severity and equally high MELD scores, women have reduced access to liver transplantation and worse outcomes compared with men. Policies addressing this disparity should consider factors beyond MELD score adjustments alone.

Racial, ethnic, and socioeconomic disparities impact post-liver transplant survival in patients with hepatocellular carcinoma

INTRODUCTION AND OBJECTIVES

Liver transplantation can be a curative treatment for patients with hepatocellular carcinoma (HCC); however, the morbidity and mortality associated with HCC varies by socioeconomic status and race and ethnicity. Policies like Share 35 were implemented to ensure equitable access to organ transplants; however, their impacts are unclear. We aimed to characterize differences in post-liver transplant (LT) survival among patients with HCC, when considering race and ethnicity, income, and insurance type, and understand if these associations were impacted by Share 35.

MATERIALS AND METHODS

We conducted a retrospective cohort study of 30,610 adult LT recipients with HCC. Data were obtained from the UNOS database. Survival analysis was carried out using Kaplan-Meier curves, and multivariate Cox regression analysis was used to calculate hazard ratios.

RESULTS

Men (HR: 0.90 (95% CI: 0.85-0.95)), private insurance (HR: 0.91 (95% CI: 0.87-0.92)), and income (HR: 0.87 (95% CI: 0.83-0.92)) corresponded with higher post-LT survival, when adjusted for over 20 demographic and clinical characteristics (Table 2). African American or Black individuals were associated with lower post-LT survival (HR: 1.20 (95% CI: 1.12-1.28)), whereas. Asian (HR: 0.79 (95% CI: 0.71-0.88)) or Hispanic (HR: 0.86 (95% CI: 0.81-0.92)) individuals were associated with higher survival as compared with White individuals (Table 2). Many of these patterns held in the pre-Share 35 and Share 35 periods.

CONCLUSIONS

Racial, ethnic, and socioeconomic disparities at time of transplant, such as private insurance and income, influence post-LT survival in patients with HCC. These patterns persist despite the passage of equitable access policies, such as Share 35.

Equity in liver transplantation: are we any closer?

PURPOSE OF REVIEW

As policies governing liver transplantation (LT) continue to change and influence clinical practice, it is important to monitor trends in equitable access and outcomes amongst patients. The purpose of this review is to closely examine recent advances and findings in health equity research in LT over the last 2 years; specifically evaluating inequities at the different stages of LT (referral, evaluation, listing, waitlist outcomes and post-LT outcomes).

RECENT FINDINGS

Advancements in geospatial analysis have enabled investigators to identify and begin to study the role of community level factors (such as neighborhood poverty, increased community capital/urbanicity score) in driving LT disparities. There has also been a shift in investigating center specific characteristics that contributes to disparities in waitlist access. Modification to the current model for end stage liver disease (MELD) score policy accounting for height differences is also crucial to eradicating the disparity in LT amongst sexes. Lastly, Black pediatric patients have been shown to have higher rates of death and worse posttransplant outcome after transitioning to adult healthcare.

SUMMARY

Although, there have been some advances in methodology and policies, inequities in waitlist access, waitlist outcomes and posttransplant outcomes continue to be pervasive in the field of LT. Future directions include expansion of social determinants of health measures, inclusion of multicenter designs, MELD score modification and investigation into drivers of worse posttransplant outcomes in Black patients.

Addressing sex-based disparities in liver transplantation

PURPOSE OF REVIEW

Disparities in access to liver transplantation by sex have been well described, disadvantaging women. Understanding the multifactorial causes of these disparities as well as the variety of proposed solutions is critical to improving access to this life-saving intervention for women. This review aims to summarize the current body of evidence on observed sex disparities in liver transplantation and highlight actionable, evidence-based mechanisms by which these disparities can be addressed.

RECENT FINDINGS

Strategies for addressing sex disparities in liver transplantation include increasing organ utilization, changing allocation policy, and leveraging public policies to reduce the incidence of end-stage liver disease. Several other promising interventions are currently being explored.

SUMMARY

In the United States, women face additional barriers to liver transplantation on the basis of sex. Immediate action is necessary to systematically address these inequities.

The effect of sex inequality on solid organ transplantation: A systematic review and meta-analysis

BACKGROUND

Sex disparities are related to biological differences, which may have significant impact on patient and allograft outcomes. The aim was to investigate the impact of sex on clinical and safety outcomes after solid organ transplantation (SOT).

METHODS

A systematic review and meta-analysis was performed. Observational studies comparing females vs. males after SOT were considered for inclusion after a systematic search of the Pubmed, Cochrane Library, and Web of Science databases conducted from 2016 to 2021. Primary outcome was mortality. PROSPERO register number: CRD42021282615.

RESULTS

After retrieving 1103 studies, 22 observational studies (1,045,380 subjects) were finally deemed eligible for inclusion. Females accounted 36.3% of SOT recipients, but presented significantly lower mortality (odds ratio (OR): 0.87, 95% confidence interval (CI): 0.83-0.92, I2=78%). In subgroup analyses, mortality was significantly lower in females undergoing liver (OR: 0.89 95%CI: 0.86-0.92, I2=0%) or kidney transplantation (OR: 0.82 95%CI: 0.76-0.89, I2=72%). Male sex was consistently reported as a protective factor against hospital readmission. Among the outcomes, allograft dysfunction was influenced by a combination of donor-recipient sex and age. Data on overall infections were inconclusive. Several reports suggest a higher risk of malignancy among males.

CONCLUSIONS

Females represent one-third of SOT recipients but have higher survival rates than males after liver and kidney transplantation. The impact on graft dysfunction was heterogeneous. While further research is warranted, our findings should encourage clinicians and researchers to consider sex as a factor when taking decisions regarding SOT management.

Proposing a Sex-Adjusted Sodium-Adjusted MELD Score for Liver Transplant Allocation

Importance

Liver allocation is determined by the model for end-stage liver disease (MELD), a scoring system based on 4 laboratory measurements. During the MELD era, sex disparities in liver transplant have increased and there are no modifications to MELD based on sex.

Objective

To use laboratory values stored in electronic health records to describe population-level sex differences in all MELD laboratory values (in healthy individuals and patients with liver disease) and propose a sex adjustment.

Design, Setting, and Participants

A retrospective cohort study was conducted from March 2019 to April 2020 to evaluate sex differences in laboratory values in liver transplant patients, patients with liver disease who did not undergo transplant, and healthy controls. Primary analyses were conducted in Vanderbilt University Medical Center (VUMC)'s deidentified electronic health record system. Replication analyses were conducted in the All of Us Research Program. Simulations of a sex-adjusted sodium-adjusted MELD (MELDNa) score were completed using liver transplant waiting list data from the liver simulated allocation modeling system. Patients who regularly used VUMC with measurements for any MELDNa component laboratory were included in the analyses. Analysis took place from November 2019 to March 2021.

Exposures

Electronic health record-reported sex.

Main Outcomes and Measure

Creatinine, bilirubin, international normalized ratio, and sodium levels.

Results

The VUMC sample was composed of 623 931 individuals (359 976 [57.7%] female) with a median (IQR) age of 44 (23-61) years. All component MELDNa laboratory values and calculated MELDNa scores yielded significant sex differences within VUMC (mean [SD] creatinine: male, 0.99 [0.39] mg/dL; female, 0.79 [0.30] mg/dL; P < .001; bilirubin: male, 0.76 [0.83] mg/dL; female, 0.58 [0.64] mg/dL; P < .001; international normalized ratio of prothrombin rate: male, 1.24 [0.42]; female, 1.20 [0.40]; P < .001; sodium: male, 139.00 [2.36] mEq/L; female, 139.03 [2.28] mEq/L; P < .001), resulting in MELDNa scoring that disadvantaged female individuals. This pattern persisted when the sample was divided into healthy controls, individuals with liver disease who did not undergo transplant, and patients who did undergo liver transplant. Female transplant patients had a greater number of decompensation traits (mean [SD]: male, 1.34 [1.11]; female, 1.60 [1.09]; P = .005), despite having lower MELDNa scores (mean [SD]: male, 21.72 [6.11]; female, 20.21 [6.15]; P = .005), indicating MELDNa scores are not accurately representing disease severity in female individuals. In simulations, the sex-adjusted MELDNa score modestly increased female transplant rate and decreased overall death.

Conclusions and Relevance

These results demonstrate pervasive sex differences in all laboratory values used in MELDNa scoring and highlight the need and utility of a sex-adjustment to the MELDNa protocol.

Mortality and Causes of Death After Liver Transplantation: Analysis of Sex Differences in a Large Nationwide Cohort

In the last few years, several studies have analyzed sex and gender differences in liver transplantation (LT), but none have performed a disaggregated analysis of both mortality and causes of death. Data from 15,998 patients, 11,914 (74.5%) males and 4,069 (25.5%) females, transplanted between 2000 and 2016 were obtained from the Liver Transplantation Spanish Registry. Survival analysis was applied to explore recipient sex as a risk factor for death. The causes of death at different follow-up duration were disaggregated by recipient sex for analysis. Short-term survival was higher in males, whereas long-term survival was higher in females. Survival at 1, 5 and 10 years post-transplant was 87.43%, 73.83%, and 61.23%, respectively, in males and 86.28%, 74.19%, and 65.10%, respectively, in females (p = 0.05). Post-LT mortality related to previous liver disease also presented sex differences. Males had 37% increased overall mortality from acute liver failure (p = 0.035) and 37% from HCV-negative cirrhosis (p < 0.001). Females had approximately 16% increased mortality when the liver disease was HCV-positive cirrhosis (p = 0.003). Regarding causes of death, non-malignancy HCV+ recurrence (6.3% vs. 3.9% of patients; p < 0.001), was more frequently reported in females. By contrast, death because of malignancy recurrence (3.9% vs. 2.2% of patients; p = 0.003) and de novo malignancy (4.8% vs. 2.5% of patients; p < 0.001) were significantly more frequent in male recipients. Cardiovascular disease, renal failure, and surgical complications were similar in both. In summary, male patients have lower short-term mortality than females but higher long-term and overall mortality. In addition, the post-LT mortality risk related to previous liver disease and the causes of mortality differ between males and females.

Portrait of Regional Trends in Liver Transplantation for Nonalcoholic Steatohepatitis in the United States

INTRODUCTION

Nonalcoholic steatohepatitis (NASH) is one of the most common etiologies of liver transplantation (LT) in the United States. We investigated regional trends in waitlist candidates, LT rates, and recipient survival among patients with NASH.

METHODS

Using the United Network for Organ Sharing database by Organ Procurement and Transplantation Network regions, we investigated waitlist registration, LT rates, and survival for NASH between January 2004 and December 2019.

RESULTS

The absolute number and percentage of total LT performed for NASH increased substantially in all Organ Procurement and Transplantation Network regions. In 2019, region 11 had the highest percentage of NASH-related LT with 31.4% followed by region 10 (25.3%) and region 8 (23.1%). Between 2015 and 2019, region 5 had the highest rising percentage in LT for NASH at 208%, followed by region 1 (194%) and region 4 (183%). The proportion of NASH hepatocellular carcinoma (NASH-HCC) was the highest in region 9 at 37.7% and lowest in region 10 (19.2%), region 3 (20.6%), and region 11 (20.8%). In multivariate analysis, diabetes (HR 1.18, P < 0.001), dialysis before LT (hazard ratio [HR] 1.53, P < 0.001), HCC (HR 1.19, P < 0.00), portal vein thrombosis (HR 1.24, P < 0.001), donor age (HR 1.026, P = 0.03), and recipient age (HR 1.24, P = <0.001) were associated with worse survival.

DISCUSSION

LT for patients with NASH has dramatically increased across all regions since 2004, but with substantial heterogeneity among regions in the proportion with HCC and post-LT survival. Identifying contributing factors to these regional differences is warranted.

Identifying and addressing disparities in the evaluation and treatment of children with growth hormone deficiency

Health disparities are a significant cause of concern globally and in the United States. Disparities have been additionally highlighted throughout the ongoing COVID-19 pandemic during which populations of color have been the most affected by the disease. Social determinants of health, race, ethnicity, and gender have all contributed to disparate outcomes and disparities spanning all age groups. Multiple socio-ecological factors contribute to disparities and different strategies have been proposed. The purpose of this paper is to provide an overview of disparities in pediatric treatment and outcomes, with a focus on children with endocrine disorders.

The influence of equitable access policies and socioeconomic factors on post-liver transplant survival

BACKGROUND

Survival following liver transplant (LT) is influenced by a variety of factors, including donor risk factors and recipient disease burden and co-morbidities. It is difficult to separate these effects from those of socioeconomic factors, such as income or insurance. The United Network for Organ Sharing (UNOS) created equitable access policies, such as Share 35, to ensure that organs are distributed to individuals with greatest medical need; however, the effect of Share 35 on disparities in post-LT survival is not clear. This study aimed to (1) characterize associations between post-transplant survival and race and ethnicity, income, insurance, and citizenship status, when adjusted for other clinical and demographic factors that may influence survival, and (2) determine if the direction of associations changed after Share 35.

METHODS

A retrospective, cohort study of adult LT recipients (n = 83,254) from the UNOS database from 2005 to 2019 was conducted. Kaplan-Meier survival graphs and stepwise multivariate cox-regression analyses were performed to characterize the effects of socioeconomic status on post-LT survival, adjusted for recipient and donor characteristics, across the time period and after Share 35.

FINDINGS

Male sex (HR: 0.93 (95% CI: 0.90-0.96)), private insurance (0.91 (0.88-0.94)), income (0.82 (0.79-0.85)), U.S. citizenship, and Asian (0.81 (0.75-0.88)) or Hispanic (0.82 (0.79-0.86)) race and ethnicity were associated with higher post-transplant survival, after adjustment for clinical and demographic factors (Table 3). These associations were found across the entire time period studied and many persisted after the implementation of Share 35 in 2013 (Table 3; male sex (0.84 (0.79-0.90)), private insurance (0.94 (0.89-1.00)), income (0.82 (0.77-0.89)), and Asian (0.87 (0.73-1.02)) or Hispanic (0.88 (0.81-0.96)) race and ethnicity).

INTERPRETATION

Recipients' socioeconomic factors at time of transplant may impact long-term post-transplant survival, and a single policy may not significantly alter these structural health inequalities.

FUNDING

None.

Correcting the sex disparity in MELD-Na

MELD-Na appears to disadvantage women awaiting liver transplant by underestimating their mortality rate. Fixing this problem involves: (1) estimating the magnitude of this disadvantage separately for each MELD-Na, (2) designing a correction for each MELD-Na, and (3) evaluating corrections to MELD-Na using simulated allocation. Using Kaplan-Meier modeling, we calculated 90-day without-transplant survival for men and women, separately at each MELD-Na. For most scores between 15 and 35, without-transplant survival was higher for men by 0-5 percentage points. We tested two proposed corrections to MELD-Na (MELD-Na-MDRD and MELD-GRAIL-Na), and one correction we developed (MELD-Na-Shift) to target the differences we quantified in survival across the MELD-Na spectrum. In terms of without-transplant survival, MELD-Na-MDRD overcorrected sex differences while MELD-GRAIL-Na and MELD-Na-Shift eliminated them. Estimating the impact of implementing these corrections with the liver simulated allocation model, we found that MELD-Na-Shift alone eliminated sex disparity in transplant rates (p = 0.4044) and mortality rates (p = 0.7070); transplant rates and mortality rates were overcorrected by MELD-Na-MDRD (p = 0.0025, p = 0.0006) and MELD-GRAIL-Na (p = 0.0079, p = 0.0005). We designed a corrected MELD-Na that eliminates sex disparities in without-transplant survival, but allocation changes directing smaller livers to shorter candidates may also be needed to equalize women's access to liver transplant.

Liver simulated allocation model does not effectively predict organ offer decisions for pediatric liver transplant candidates

The SRTR maintains the liver-simulated allocation model (LSAM), a tool for estimating the impact of changes to liver allocation policy. Integral to LSAM is a model that predicts the decision to accept or decline a liver for transplant. LSAM implicitly assumes these decisions are made identically for adult and pediatric liver transplant (LT) candidates, which has not been previously validated. We applied LSAM's decision-making models to SRTR offer data from 2013 to 2016 to determine its efficacy for adult (≥18) and pediatric (<18) LT candidates, and pediatric subpopulations-teenagers (≥12 to <18), children (≥2 to <12), and infants (<2)-using the area under the receiver operating characteristic (ROC) curve (AUC). For nonstatus 1A candidates, all pediatric subgroups had higher rates of offer acceptance than adults. For non-1A candidates, LSAM's model performed substantially worse for pediatric candidates than adults (AUC 0.815 vs. 0.922); model performance decreased with age (AUC 0.898, 0.806, 0.783 for teenagers, children, and infants, respectively). For status 1A candidates, LSAM also performed worse for pediatric than adult candidates (AUC 0.711 vs. 0.779), especially for infants (AUC 0.618). To ensure pediatric candidates are not unpredictably or negatively impacted by allocation policy changes, we must explicitly account for pediatric-specific decision making in LSAM.

His and her mathematical models of physiological systems

Beyond the reproductive system and reproductive behaviors, men and women exhibit major differences in many organ systems, including the anatomy of the brain, the activities of the stress and immune systems, and the metabolic and cardiovascular functions. A comprehensive understanding of the impact of these sex differences on health and disease is crucial to the development of effective sex-based therapies. Mathematical modeling has the potential of facilitating and contributing to advancing the understanding of sex differences in health and disease. Indeed, explosion of mathematical models have been developed in recent decades for different aspects of human physiology and pathophysiology. This review contains a survey of sex-specific mathematical models of physiological systems, describe insights that have been revealed in those modeling studies, and discuss future opportunities.