The Dangerous Precedent of Censoring Scientific Dissemination.

The American Transplant Congress (ATC) is the largest national transplant meeting in the United States jointly sponsored by the American Society of Transplantation and the American Society of Transplant Surgeons. The 2024 ATC was held in Philadelphia, Pennsylvania during which a number of peer-reviewed scientific abstracts were censored from the program by the Health Resources and Services Administration (HRSA). These abstract presentations were redacted from the program for perceived conflict with current government policy effectively restricting dissemination of highly rated findings and discussion in a scientific forum. In this viewpoint we describe the content of the abstracts that were withdrawn from the annual ATC meeting and the implications of this censorship by HRSA. We further consider the ramifications of this action for prospective evaluation of government policy and the relationship of the contract agency with the transplant community in the context of ongoing discussions of modernizing the transplant system which has previously been critiqued for lack of transparency.

Augmenting the Unites States transplant registry with external mortality data: A moving target ripe for further improvement.

The Organ Procurement and Transplantation Network conducts a robust death verification process when augmenting the United States transplant registry with external sources of data. Process enhancements added over 35,000 externally verified deaths across waitlist candidates and transplant recipients for all organs beginning in April 2022. Ninety-four percent of added posttransplant deaths occurred beyond 5 years posttransplant, and over 74% occurred beyond 10 years. Deceased donor solid organ recipients transplanted from January 1, 2010, through October 31, 2020, were analyzed from January and July 2022 Organ Procurement and Transplantation Network Standard Transplant Analysis and Research and the Scientific Registry of Transplant Recipients Standard Analysis Files to quantify the impact of including vs excluding unverified deaths (not releasable to researchers) on posttransplant patient survival estimates. Across all organs, 1- and 5-year posttransplant survival rates were not substantially impacted; meaningful differences were observed in 10-year survival among kidney recipients. These findings bear important implications for anyone who utilized transplant registry data to examine long-term outcomes prior to the updated verification process. Users of transplant surveillance data should interpret results of long-term outcomes cautiously, particularly differences across subpopulations, and the transplant community should identify ways to improve data quality and minimize the reporting burden on transplant institutions.

Applying propensity methods to the United States transplant registry for external real-world evidence control arms for 5-year survival in the BENEFIT study.

To address the challenges of assessing the impact of a reasonably likely surrogate endpoint on long-term graft survival in prospective kidney transplant clinical trials, the Transplant Therapeutics Consortium established a real-world evidence workgroup evaluating the scientific value of using transplant registry data as an external control to supplement the internal control group. The United Network for Organ Sharing retrospectively simulated the use of several distinct contemporaneous external control groups, applied multiple cause inference methods, and compared treatment effects to those observed in the BENEFIT study. Applying BENEFIT study enrollment criteria produced a smaller historical cyclosporine control arm (n = 153) and a larger, alternative (tacrolimus) historical control arm (n = 1069). Following covariate-balanced propensity scoring, Kaplan-Meier 5-year all-cause graft survivals were 81.3% and 81.7% in the Organ Procurement and Transplantation Network (OPTN) tacrolimus and cyclosporine external control arms, similar to 80.3% observed in the BENEFIT cyclosporine treatment arm. Five-year graft survival in the belatacept-less intensive arm was significantly higher than the OPTN controls using propensity scoring for comparing cyclosporine and tacrolimus. Propensity weighting using OPTN controls closely mirrored the BENEFIT study's long-term control (cyclosporine) arm's survival rate and the less intensive arm's treatment effect (significantly higher survival vs control). This study supports the feasibility and validity of using supplemental external registry controls for long-term survival in kidney transplant clinical trials.

The impact of high volumes of COVID-related lung transplant on waitlist mortality for non-COVID candidates in the United States.

Some patients with coronavirus disease 19 (COVID) develop serious, irreversible lung disease, including acute respiratory distress syndrome or pulmonary fibrosis. For select candidates, lung transplant is the only option to improve quality and length of life. Because of the severity of end-stage COVID-related lung disease, these candidates receive high allocation priority in the United States, including higher priority than many patients without COVID-related lung disease. This study assessed whether transplant centers with a large volume of COVID-related lung transplants experienced an increase in waitlist mortality for non-COVID transplant candidates. Nineteen centers were included as high-volume programs, defined as being in the top third of centers who transplanted COVID patients. Of the 2867 non-COVID patients waitlisted at these centers, there was no significant difference in waitlist mortalities of non-COVID transplant candidates between the pre-COVID transplant era (January 2018-February 2020) and during the period of high COVID transplant volume (March 2020-October 2022) (subhazard ratio: .92 [95% CI = .81-1.05], p = .22). Among high volume centers, the decision to transplant and to prioritize patients with COVID-related lung disease did not significantly impact the waitlist mortality of other candidates.

Effect of the opioid crisis on the liver transplantation donor pool: A national analysis.

BACKGROUND: Over the last decade there has been a surge in overdose deaths due to the opioid crisis. We sought to characterize the temporal change in overdose donor (OD) use in liver transplantation (LT), as well as associated post-LT outcomes, relative to the COVID-19 era. METHODS: LT candidates and donors listed between January 2016 and September 2022 were identified from the Scientific Registry of Transplant Recipients database. Trends in LT donors and changes related to OD were assessed pre- versus post-COVID-19 (February 2020). RESULTS: Between 2016 and 2022, most counties in the United States experienced an increase in overdose-related deaths (n = 1284, 92.3%) with many counties (n = 458, 32.9%) having more than a doubling in drug overdose deaths. Concurrently, there was an 11.2% increase in overall donors, including a 41.7% increase in the number of donors who died from drug overdose. In pre-COVID-19 overdose was the 4th top mechanism of donor death, while in the post-COVID-19 era, overdose was the 2nd most common cause of donor death. OD was younger (OD: 35 yrs, IQR 29-43 vs. non-OD: 43 yrs, IQR 31-56), had lower body mass index (≥35 kg/cm2, OD: 31.2% vs. non-OD: 33.5%), and was more likely to be HCV+ (OD: 28.9% vs. non-OD: 5.4%) with lower total bilirubin (≥1.1 mg/dL, OD: 12.9% vs. non-OD: 20.1%) (all p < .001). Receipt of an OD was not associated with worse graft survival (HR .94, 95% CI .88-1.01, p = .09). CONCLUSIONS: Opioid deaths markedly increased following the COVID-19 pandemic, substantially altering the LT donor pool in the United States.

1-Year Outcomes of Lung Transplantation for Coronavirus Disease 2019-Associated End-Stage Lung Disease in the United States.

BACKGROUND: Lung transplantation can provide quality of life and survival benefits for patients with coronavirus disease 2019 (COVID-19)-associated end-stage lung disease. Characteristics and outcomes of these lung transplant recipients are limited to mostly single-center experiences or provide a short-term follow-up. METHODS: Characteristics of deceased donors and adult lung transplant recipients for COVID-19-associated end-stage lung disease between August-2020 and June-2022 were analyzed using deidentified United Network for Organ Sharing database. Post-transplant patient survival of COVID-19 recipients was analyzed and compared with non-COVID-19 recipients. Secondary outcomes were length of hospitalization, post-transplant complications, and rates of organ rejection. RESULTS: During the study period, 400 lung transplants for COVID-associated end-stage lung disease comprised 8.7% of all lung transplants performed in United States. In the COVID-19 group, Hispanic males received lung transplants at significantly higher rates. The COVID-19 group was younger and had greater need for intensive care unit stay, mechanical ventilation, hemodialysis, extracorporeal membrane oxygenation support, and receipt of antibiotics pre-lung transplant. They had higher lung allocation score, with a shorter wait-list time and received more double lung transplants compared with non-COVID-19 recipients. Post-transplant, the COVID-19 cohort had longer hospital stays, with similar 1-year patient survival (COVID, 86.6% vs non-COVID, 86.3%). Post-transplant, COVID-19-associated deaths were 9.2% of all deaths among lung transplant recipients. CONCLUSIONS: Lung transplantation offers a effective option for carefully selected patients with end-stage lung disease from prior COVID-19, with short-term and long-term outcomes similar to those for lung transplant recipients of non-COVID-19 etiology.

Impact of donor kidney biopsy on kidney yield and posttransplant outcomes.

Procurement biopsy is performed to determine kidney quality, but evidence supporting such association is poor. We investigated the impact of glomerulosclerosis percentage (GS%) on kidney yield and patient outcomes. Information on deceased kidney donors from July 1, 2017, to June 30, 2019, was collected. Association between GS% and kidney yield (number of kidneys procured per donor) and posttransplant graft and patient outcomes were studied. Maximal GS% and minimal GS% were calculated to determine the relationship between GS% and kidney yield; minimal GS% only for correlation with posttransplant outcomes. Multinomial logistic regression and Cox models with least absolute shrinkage and selection operator were used to analyze the association of GS% with kidney yield and posttransplant outcomes, respectively. The kidney yield was 1.63 when maximal GS% and minimal GS% were <5%, but was 0.88 when both GS% were >20%. The hazard ratio for graft failure 1 year after transplant was 1.05 when minimal GS% was 16% to 20%, but was 1.3 for GS% of >20%. The hazard ratio for mortality increased from 1 to 1.2 when minimal GS% reached >20%. In summary, higher GS% was associated with lower kidney yield and inferior posttransplant outcomes. Incorporation of GS% into Scientific Registry of Transplant Recipients models may reassure organ procurement organizations and transplant centers pursuing kidneys with relatively high GS% levels, thereby reducing kidney discard rates.

Mortality among solid organ transplant recipients with a pretransplant cancer diagnosis.

Little is known about the outcomes among solid organ transplant recipients with a pretransplant cancer diagnosis. We used linked data from the Scientific Registry of Transplant Recipients with 33 US cancer registries. Cox proportional hazards models assessed associations of pretransplant cancer with overall mortality, cancer-specific mortality, and development of a new posttransplant cancer. Among 311 677 recipients, the presence of a single pretransplant cancer was associated with increased overall mortality (adjusted hazard ratio [aHR], 1.19; 95% CI, 1.15-1.23) and cancer-specific mortality (aHR, 1.93; 95% CI, 1.76-2.12); results for 2+ pretransplant cancers were similar. Cancer-specific mortality was not significantly increased for uterine, prostate, or thyroid cancers (aHRs were 0.83, 1.22, and 1.54, respectively) but strongly elevated for lung cancer and myeloma (aHRs were 3.72 and 4.42, respectively). A pretransplant cancer diagnosis was also associated with increased risk of developing posttransplant cancer (aHR, 1.32; 95% CI, 1.23-1.40). Among 306 recipients whose cancer death was confirmed by cancer registry data, 158 deaths (51.6%) were from a de novo posttransplant cancer and 105 (34.3%) from the pretransplant cancer. Pretransplant cancer diagnoses are associated with increased mortality after transplantation, but some deaths are related to posttransplant cancers and other causes. Improved candidate selection and cancer screening and prevention may reduce mortality in this population.

Improving equity in kidney transplant allocation policies through a novel genetic metric: The Matched Donor Potential.

The demand for donors' kidneys continues to increase amid a shortage of available donors. Managing policies to thoughtfully allocate this scarce resource is a complex process. Although human leukocyte antigen (HLA) matching has been shown to prolong graft survival, its relative contribution to allocation schemes is empirically compromised owing to competing priorities. We explored using a new metric, Matched Donor Potential (MDP), to facilitate improved HLA matching while promoting equity. We interrogated all active kidney waitlist patients (N = 164 427), their corresponding unacceptable antigen files, and all effective donors in the Scientific Registry of Transplant Recipients (January 1, 2016-December 31, 2017). Cause-specific hazard functions were evaluated to assess the potential impact of the MDP metric on deceased donor transplant access rates for all candidates. Access was affected by ethnicity, blood group type, and calculated Panel Reactive Antibody (cPRA). Importantly, we show that access to transplantation is influenced by the patient's own HLA makeup regardless of their ethnicity and by the HLA makeup of effective donors. The MDP metric demonstrates a high association with access to transplantation. Adjusting Cox models to include this new metric resulted in improved access to kidney transplantation for waitlist candidates of minority heritage while significantly promoting HLA matching. Thus, the MDP metric accounts for balanced, equitable organ allocation algorithms.

Factors enabling transplant program participation in the Scientific Registry of Transplant Recipients (SRTR) Living Donor Collective: A national survey.

BACKGROUND: The Scientific Registry of Transplant Recipients (SRTR) Living Donor Collective (LDC), the first effort to create a lifetime registry for living donor candidates in the United States, requires transplant programs to register donor candidates while the SRTR conducts follow-up. METHODS: To better understand facilitators and barriers to program participation, we conducted a brief electronic survey of U.S. transplant program staff from October 26, 2021 to December 17, 2021. RESULTS: We received 132 responses, with at least one response from 87 living donor programs (46 kidney programs, 33 kidney and liver programs, and eight liver programs alone). We found 86% of program representatives strongly agreed or agreed that funding adequate to cover the cost of data collection would facilitate LDC participation, 92% agreed or strongly agreed with importance of electronic data submission options, and 74% reported that elimination of requirements to submit duplicative pre-operative information to the Organ Procurement and Transplantation Network (OPTN) would be helpful. Other potentially enabling factors include reduction in duration of OPTN postdonation follow-up requirements, ease-of-use, protection from data use for regulation, adequate data security, and equity in data access. CONCLUSION: This survey identifies potential targets to strengthen participation in the effort to create a national living donor registry in the United States. Collaboration and investment to overcome barriers to LDC participation among transplant programs are vital to generate long-term data on living donation for donor candidates, donors, and patients in need of transplant.

The real unmet need: A multifactorial approach for identifying sensitized kidney candidates with low access to transplant.

BACKGROUND: At the start of 2020, the kidney waiting list consisted of 2526 candidates with a calculated panel reactive antibody (CPRA) of 99.9% or greater, a cohort demonstrated in published research to have meaningfully lower than average access to transplantation even under the revised kidney allocation system (KAS). METHODS: This was a retrospective analysis of US kidney registrations using data from the OPTN [Reference (https://optn.transplant.hrsa.gov/data/about-data/)]. The period-prevalent study cohort consisted of US kidney-alone registrations who waited at least 1 day between April 1, 2016, when HLA DQ-Alpha and DP-Beta unacceptable antigen data became available in OPTN data collection, to December 31, 2019. Poisson rate regression was used to model deceased donor kidney transplant rates per active year waiting and using an offset term to account for differential at-risk periods. Median time to transplant was estimated for each IRR group using the Kaplan-Meier method. Sensitivity analyses were included to address geographic variation in supply-to-demand ratios and differences in dialysis time or waiting time. RESULTS: In this study, we found 1597 additional sensitized (CPRA 50-<99.9%) candidates with meaningfully lower than average access to transplant when simultaneously taking into account CPRA and other factors. In combination with CPRA, candidate blood type, Estimated Post-Transplant Survival Score (EPTS), and presence of other antibody specificities beyond those in the current, 5-locus CPRA were found to influence the likelihood of transplant. CONCLUSION: In total, this suggests approximately 4100 sensitized candidates are on the waiting list who represent a community of disadvantaged patients who may benefit from progressive therapies and interventions to facilitate incompatible transplantation. Though associated with higher risks, such interventions may nevertheless be more attractive than remaining on dialysis with the associated accumulation of mortality risk over time.

Mortality and Morbidity Among Adult Liver Retransplant Recipients.

BACKGROUND: Liver transplantation (LT) is life-saving procedure for patients with end-stage liver failure with up to 20% of patients suffering graft failure following primary transplantation. Retransplantation (ReLT) remains the only definitive treatment for irreversible graft failure. AIMS: We aimed to explore the postoperative outcomes following liver ReLT. METHODS: Patients who had received a liver transplant between 2003 and 2016 were retrospectively identified using the Scientific Registry of Transplant Recipients (SRTRs). Patients were stratified based on previous liver transplant history. The primary outcomes of this study were 5-year postoperative mortality, morbidity, and length of hospital stay following LT. RESULTS: 60,554 (96%) recipients were first LT recipients and 2524 (4%) were ReLT recipients. Compared with first LT, ReLT recipients had significantly higher rates of mortality (OR 1.93, 95%CI 1.76-2.12), overall morbidity (OR 1.80, 95%CI 1.65-1.96), and prolonged length of stay (OR 1.66, 95%CI 1.52-1.81) on multivariate analysis. Morbidity including cardiovascular (CVD) complications (OR 1.32, 95%CI 1.08-1.60), graft failure (OR 2.18, 95%CI 1.84-2.57), infection (OR 2.13, 95%CI 1.82-2.50), and hemorrhage (OR 2.67, 95%CI 2.00-3.61) were significantly greater in ReLT recipients. Compared to first LT, ReLT patients had a significant increase in overall 5-year mortality (p < 0.001), 5-year mortality due to CVD complications (p < 0.001), infection (p = 0.009), but not graft failure (p = 0.3543). CONCLUSION: ReLT is associated with higher rates of 5-year mortality, overall morbidity, CVD morbidity, infection, and graft failure. Higher 5-year mortality in ReLT is due to CVD and infections. These results could be used in preoperative patient assessment and prognostic counseling for ReLT.

Kidney transplant candidacy evaluation and waitlisting practices in the United States and their association with access to transplantation.

There are limited data on the degree of variability in practices surrounding prioritization of referrals for transplant evaluation and criteria for transplant candidacy and their association with transplantation rates. We surveyed transplant programs across the United States between January 2020 and May 2020 to determine current pre-transplantation practices. We examined the relation between these reported practices and the outcomes of waitlisted patients at responding programs between January 2015 and March 2021 using Scientific Registry of Transplant Recipients data. We used adjusted Cox models with random effects to accommodate clustering by program. Primary outcomes included living or deceased donor transplantation. Of 172 surveyed programs, 90 participated. Substantial variations were noted in when the candidacy evaluation began (13% reported when eGFR was <30 mL/min/1.73 m2 and 17% reported no set policy) and the approach to pre-transplantation cardiac workup (multi-modality [58%], stress echocardiogram [20%]). Using adjusted models, a program policy of using other measures of body habitus to determine transplant candidacy rather than requiring patients to meet a body mass index (BMI) threshold of ≤35 kg/m2 (reference group) for candidacy was associated with a higher hazard of living donor transplantation (HR 1.83 [95% CI 1.10-3.03]). Pre-transplant practices vary substantially across the United States, and select practices were associated with transplantation rates.

COVID-19 and transplantation-Data censoring.

During the early wave of the COVID-19 pandemic, the Scientific Registry of Transplant Recipients (SRTR) designated a "black out" period between March 12, 2020, and June 12, 2020, for transplant outcomes reporting. We discuss the implications and potential bias it has introduced as it may selectively favor the outcomes for certain regions and harm other regions due to varied effects of different waves of COVID-19 infections across the United States.

Listing at non-local transplant centers is associated with increased access to deceased donor kidney transplantation.

The ability of kidney transplant candidates to travel outside of their usual place of care varies by sociodemographic factors, potentially exacerbating disparities in access. We used Transplant Referral Regions (TRRs) to overcome previous methodological barriers of using geographic distance to assess the characteristics and outcomes of patients listed for kidney transplant at centers in neighboring TRR or beyond neighboring TRRs. Among listed kidney transplant candidates, 20.9% traveled to a neighbor and 5.6% beyond a neighbor. A higher proportion of travelers were White, had some college education, and lived in ZIP codes with lower poverty. Travel to a neighbor was associated with a 7% increase in likelihood of deceased donor transplant (cHR: 1.07, 95% CI: 1.05, 1.09) and traveling beyond a neighbor with a 19% increase (cHR: 1.19, 95% CI: 1.15, 1.24). Travelers had similar rates of living donor transplant and waitlist mortality as patients who did not travel; those who traveled beyond a neighbor had slightly lower posttransplant mortality (HR: 0.91, 95% CI: 0.83, 0.99). In conclusion, the ability to travel outside of the recipient's assigned TRR increases access to transplantation and improves long-term survival.

Transplant program evaluations in the middle of the COVID-19 pandemic.

Potential regional variations in effects of COVID-19 on federally mandated, program-specific evaluations by the Scientific Registry of Transplant Recipients (SRTR) have been controversial. SRTR January 2022 program evaluations ended transplant follow-up on March 12, 2020, and excluded transplants performed from March 13, 2020 to June 12, 2020 (the "carve-out"). This study examined the carve-out's impact, and the effect of additionally censoring COVID-19 deaths, on first-year posttransplant outcomes for transplants from July 2018 through December 2020. Program-specific hazard ratios (HRs) for graft failure and death estimated under two alternative scenarios were compared with published HRs: (1) the carve-out was removed; (2) the carve-out was retained, but deaths due to COVID-19 were additionally censored. The HRs estimated by censoring COVID-19 deaths were highly correlated with those estimated with the carve-out alone (r2  = .96). Removal of the carve-out resulted in greater variation in HRs while remaining highly correlated (r2  = .82); however, little geographic impact of the carve-out was observed. The carve-out increased average HR in the Northwest by 0.049; carve-out plus censoring reduced average HR in the Midwest by 0.009. Other regions of the country were not significantly affected. Thus, the current COVID-19 carve-out does not appear to impart substantial bias based on the region of the country.

Social determinants of health data in solid organ transplantation: National data sources and future directions.

Health equity research in transplantation has largely relied on national data sources, yet the availability of social determinants of health (SDOH) data varies widely among these sources. We sought to characterize the extent to which national data sources contain SDOH data applicable to end-stage organ disease (ESOD) and transplant patients. We reviewed 10 active national data sources based in the United States. For each data source, we examined patient inclusion criteria and explored strengths and limitations regarding SDOH data, using the National Institutes of Health PhenX toolkit of SDOH as a data collection instrument. Of the 28 SDOH variables reviewed, eight-core demographic variables were included in ≥80% of the data sources, and seven variables that described elements of social status ranged between 30 and 60% inclusion. Variables regarding identity, healthcare access, and social need were poorly represented (≤20%) across the data sources, and five of these variables were included in none of the data sources. The results of our review highlight the need for improved SDOH data collection systems in ESOD and transplant patients via: enhanced inter-registry collaboration, incorporation of standardized SDOH variables into existing data sources, and transplant center and consortium-based investigation and innovation.

An updated estimate of posttransplant survival after implementation of the new donor heart allocation policy.

The Organ Procurement and Transplant Network (OPTN) implemented a new heart allocation policy on October 18, 2018. Published estimates of lower posttransplant survival under the new policy in cohorts with limited follow-up may be biased by informative censoring. Using the Scientific Registry of Transplant Recipients, we used the Kaplan-Meier method to estimate 1-year posttransplant survival for pre-policy (November 1, 2016, to October 31, 2017) and post-policy cohorts (November 1, 2018, to October 31, 2019) with follow-up through March 2, 2021. We adjusted for changes in recipient population over time with a multivariable Cox proportional hazards model. To demonstrate the effect of inadequate follow-up on post-policy survival estimates, we repeated the analysis but only included follow-up through October 31, 2019. Transplant programs transplanted 2594 patients in the pre-policy cohort and 2761 patients in the post-policy cohort. With follow-up through March 2, 2021, unadjusted 1-year posttransplant survival was 90.6% (89.5%-91.8%) in the pre-policy cohort and 90.8% (89.7%-91.9%) in the post-policy cohort (adjusted HR = 0.93 [0.77-1.12]). Ignoring follow-up after October 31, 2019, the post-policy estimate was biased downward (1-year: 82.2%). When estimated with adequate follow-up, 1-year posttransplant survival under the new heart allocation policy was not significantly different.

Place-based heterogeneity in lung transplant recipient outcomes.

Place is defined as a social or environmental area of residence with meaning to a patient. We hypothesize there is an association between place and the clinical outcomes of lung transplant recipients in the United States. In a retrospective cohort study of transplants between January 1, 2010, and December 31, 2019, in the Scientific Registry of Transplant Recipients, multivariable Cox regression models were used to test the association between place (through social and environmental factors) with readmission, lung rejection, and survival. Among 18,465 recipients, only 20% resided in the same county as the transplant center. Recipients from the most socially vulnerable counties when compared to the least vulnerable were more likely to have COPD as a native disease, Black or African American race, and travel long distances to reach a transplant center. Higher local life expectancy was associated with lower likelihood for readmission (odds ratio [OR] = 0.90, 95% confidence interval [CI]: 0.84, 0.98, p = .01). Higher social vulnerability was associated with a higher likelihood of lung rejection (OR = 1.37, [CI]: 1.07, 1.76, p = .01). There was no association of residence with posttransplant survival. Recipient place-based factors were associated with complications and processes of care after transplant and warrant further investigation.

Center-level and region-level variations in liver transplantation practices following acuity circles policy change.

Although early studies suggest the Acuity Circles (AC) allocation policy has increased access to deceased donor liver transplants (DDLTs) for patients with the highest MELD scores, changes in center- and region-level practices among patients with the highest MELD scores in response to AC are not well-characterized. OPTN/UNOS data were analyzed to compare center-level changes in the number of DDLTs based on allocation-MELD (aMELD) categories used for AC sharing performed in the 18-month periods before and after AC enactment on February 4, 2020. There was large center-level variation in the number and proportion of aMELD ≥ 37 DDLTs performed from pre-AC to AC period; 13 centers accounted for 196 of the 198 total net increase in aMELD ≥ 37 DDLTs performed after AC, 5 of these being from UNOS region 5. Similar center-level variation was seen for MELD 33-36 and MELD 29-32 DDLTs, with 17 centers and 14 centers, respectively, accounting for the entire net increase in DDLTs in the aMELD categories. In conclusion, AC increased access to livers for transplantation for high MELD patients nationally, but imbalances remain in transplant practice patterns at the center and regional levels. Longer-term study is necessary to assess effectiveness of AC in improving equitability of liver transplantations.