Big data in organ transplantation: registries and administrative claims

To decline or not to decline: Consequences of decision-making regarding lung offers from donors with hepatitis C

OBJECTIVE

Lung transplants from donors with hepatitis C (HCV D+) have excellent outcomes, but these organs continue to be declined. We evaluated whether (1) being listed to consider and (2) accepting versus declining HCV D+ offers provided a survival benefit to lung transplant candidates.

METHODS

Using the Scientific Registry of Transplant Recipients, we identified all adult (≥18 years) lung transplant candidates 2016-2021 and compared waitlist mortality between those willing versus not willing to consider HCV D+ offers using competing risk regression. We identified all candidates offered an HCV D+ lung that was later accepted and followed them from offer decision until death or end-of-study. We estimated adjusted mortality risk of accepting versus declining an HCV D+ lung offer using propensity-weighted Cox regression.

RESULTS

From 2016 to 2021, we identified 21,007 lung transplant candidates, 33.8% of whom were willing to consider HCV D+ offers. Candidates willing to consider HCV D+ offers had a 17% lower risk of waitlist mortality (subhazard ratio, 0.83; 95% confidence interval, 0.75-0.91, P < .001). Over the same period, 665 HCV D+ lung offers were accepted after being declined a total of 2562 times. HCV D+ offer acceptance versus decline was associated with a 20% lower risk of mortality (adjusted hazard ratio, 0.80; 95% confidence interval, 0.66-0.96, P = .02).

CONCLUSIONS

Considering HCV D+ lung offers was associated with a 17% lower risk of waitlist mortality, whereas accepting versus declining an HCV D+ lung offer was associated with a 20% lower risk of mortality. Centers and candidates should consider accepting suitable HCV D+ lung offers to optimize outcomes.

Organ Nonutilization Following Revision to the Public Health Service Donor Risk Criteria for HIV, HCV, or HBV Transmission

BACKGROUND

Organs from Public Health Service criteria (PHSC) donors, previously referred to as PHS infectious-risk donors, have historically been recovered but not used, traditionally referred to as "discard," at higher rates despite negligible risk to recipients. On March 1, 2021, the definition of PHSC donors narrowed to include only the subset of donors deemed to have meaningfully elevated risk in the current era of improved infectious disease testing.

METHODS

Using Scientific Registry of Transplant Recipients data from May 1, 2019, to December 31, 2022, we compared rates of PHSC classification and nonutilization of PHSC organs before versus after the March 1, 2021, policy change among recovered decedents using the χ 2 tests. We performed an adjusted interrupted time series analysis to examine kidney and liver recovery/nonuse (traditionally termed "discard") and kidney, liver, lung, and heart nonutilization (nonrecovery or recovery/nonuse) prepolicy versus postpolicy.

RESULTS

PHSC classification dropped sharply from 24.5% prepolicy to 15.4% postpolicy ( P  < 0.001). Before the policy change, PHSC kidney recovery/nonuse, liver nonuse, lung nonuse, and heart nonuse were comparable to non-PHSC estimates (adjusted odds ratio: kidney =  0.98 1.06 1.14 , P  = 0.14; liver =  0.85 0.92 1.01 , P  = 0.07; lung =  0.91 0.99 1.08 , P  = 0.83; heart =  0.89 0.97 1.05 , P  = 0.47); following the policy change, PHSC kidney recovery/nonuse, liver nonuse, lung nonuse, and heart nonuse were lower than non-PHSC estimates (adjusted odds ratio: kidney =  0.77 0.84 0.91 , P  < 0.001; liver =  0.77 0.84 0.92 , P  < 0.001; lung =  0.74 0.81 0.90 , P  < 0.001; heart =  0.61 0.67 0.73 , P  < 0.001).

CONCLUSIONS

Even though PHSC donors under the new definition are a narrower and theoretically riskier subpopulation than under the previous classification, PHSC status appears to be associated with a reduced risk of kidney and liver recovery/nonuse and nonutilization of all organs. Although historically PHSC organs have been underused, our findings demonstrate a notable shift toward increased PHSC organ utilization.

National Incidence, Outcomes, and Management Strategies for Pre- and Post-Transplant Atrial Fibrillation in Heart Transplant Recipients

Background

Among heart transplant candidates, atrial fibrillation (AF) is a common comorbidity; however, little is known about the impact of pre-transplant AF on incidence of post-transplant AF or other transplant outcomes.

Methods

Adult heart transplant recipients transplanted from 07/01/2012 to 07/01/2021 with data available in both the Scientific Registry of Transplant Recipients and Symphony Health pharmacy databases were included. Recipients were categorized by presence of pre-transplant AF using prescription fill data. Perioperative outcomes and survival out to 5 years post-transplant were compared between those with and without pre-transplant AF.

Results

Of the 11,789 heart transplant recipients, 2,477 (21.0%) had pre-transplant AF. Pre-transplant AF was associated with an increased likelihood of pre-discharge stroke (aOR 2.13 [95%CI: 1.07-4.26], p=0.03) and dialysis (aOR 1.45 [1.05-2.00], p=0.02), as well as of post-transplant AF at 6 months (aOR 2.42 [1.44-1.48], p=0.001) and 1 year (aOR 2.81 [1.72-4.56], p<0.001). Pre-transplant AF was associated with increased post-transplant mortality at 30 days (aHR 2.39 [1.29-4.44], p=0.006) and 1 year (aHR 1.46 [95% CI: 1.01-2.13], p=0.04), but similar mortality at 5 years (aHR 1.23 [0.96-1.58], p=0.11).

Conclusion

Heart transplant recipients with pre-transplant AF had worse short-term outcomes and increased risk of developing post-transplant AF but comparable survival at 5 years post-transplant. Our findings emphasize the importance of increased monitoring for perioperative complications and highlight the long-term safety of heart transplantation in this population.

What Is New?

Patients with atrial fibrillation who undergo heart transplantation have worse short term survival (30-days and 1-year) but similar long term survival (5-years) compared to recipients without pre-transplant atrial fibrillation.Pre-transplant atrial fibrillation increases the risk of clinically significant post-transplant atrial fibrillation and peri-operative stroke.Rate vs rhythm control pharmacotherapy for atrial fibrillation is not associated with differences in survival in heart transplant recipients with pre-transplant atrial fibrillation.

What are the Clinical Implications?

Atrial fibrillation should not deter heart transplantation in appropriate candidates, though cardiovascular and stroke risk adjustment may be warranted.Use of amiodarone at doses ≤ 200 mg/day is not associated with reduced survival in heart transplant recipients with pre-transplant atrial fibrillation.

Design, cohort profile and comparison of the KTD-Innov study: a prospective multidimensional biomarker validation study in kidney allograft rejection

There is an unmet need for robust and clinically validated biomarkers of kidney allograft rejection. Here we present the KTD-Innov study (ClinicalTrials.gov, NCT03582436), an unselected deeply phenotyped cohort of kidney transplant recipients with a holistic approach to validate the clinical utility of precision diagnostic biomarkers. In 2018-2019, we prospectively enrolled consecutive adult patients who received a kidney allograft at seven French centers and followed them for a year. We performed multimodal phenotyping at follow-up visits, by collecting clinical, biological, immunological, and histological parameters, and analyzing a panel of 147 blood, urinary and kidney tissue biomarkers. The primary outcome was allograft rejection, assessed at each visit according to the international Banff 2019 classification. We evaluated the representativeness of participants by comparing them with patients from French, European, and American transplant programs transplanted during the same period. A total of 733 kidney transplant recipients (64.1% male and 35.9% female) were included during the study. The median follow-up after transplantation was 12.3 months (interquartile range, 11.9-13.1 months). The cumulative incidence of rejection was 9.7% at one year post-transplant. We developed a distributed and secured data repository in compliance with the general data protection regulation. We established a multimodal biomarker biobank of 16,736 samples, including 9331 blood, 4425 urinary and 2980 kidney tissue samples, managed and secured in a collaborative network involving 7 clinical centers, 4 analytical platforms and 2 industrial partners. Patients' characteristics, immune profiles and treatments closely resembled those of 41,238 French, European and American kidney transplant recipients. The KTD-Innov study is a unique holistic and multidimensional biomarker validation cohort of kidney transplant recipients representative of the real-world transplant population. Future findings from this cohort are likely to be robust and generalizable.

A2/A2B to B deceased donor kidney transplantation in the Kidney Allocation System era

Kidney transplantation from blood type A2/A2B donors to type B recipients (A2→B) has increased dramatically under the current Kidney Allocation System (KAS). Among living donor transplant recipients, A2-incompatible transplants are associated with an increased risk of all-cause and death-censored graft failure. In light of this, we used data from the Scientific Registry of Transplant Recipients from December 2014 until June 2022 to evaluate the association between A2→B listing and time to deceased donor kidney transplantation (DDKT) and post-DDKT outcomes for A2→B recipients. Among 53 409 type B waitlist registrants, only 12.6% were listed as eligible to accept A2→B offers ("A2-eligible"). The rates of DDKT at 1-, 3-, and 5-years were 32.1%, 61.4%, and 72.1% among A2-eligible candidates and 14.1%, 29.9%, and 44.1% among A2-ineligible candidates, with the former experiencing a 133% higher rate of DDKT (Cox weighted hazard ratio (wHR) = 2.192.332.47; P < .001). The 7-year adjusted mortality was comparable between A2→B and B-ABOc (type B/O donors to B recipients) recipients (wHR 0.780.941.13, P = .5). Moreover, there was no difference between A2→B vs B-ABOc DDKT recipients with regards to death-censored graft failure (wHR 0.771.001.29, P > .9) or all-cause graft loss (wHR 0.820.961.12, P = .6). Following its broader adoption since the implementation of the kidney allocation system, A2→B DDKT appears to be a safe and effective transplant modality for eligible candidates. As such, A2→B listing for eligible type B candidates should be expanded.

Neighborhood Segregation and Access to Live Donor Kidney Transplantation

Importance

Identifying the mechanisms of structural racism, such as racial and ethnic segregation, is a crucial first step in addressing the persistent disparities in access to live donor kidney transplantation (LDKT).

Objective

To assess whether segregation at the candidate's residential neighborhood and transplant center neighborhood is associated with access to LDKT.

Design, Setting, and Participants

In this cohort study spanning January 1995 to December 2021, participants included non-Hispanic Black or White adult candidates for first-time LDKT reported in the US national transplant registry. The median (IQR) follow-up time for each participant was 1.9 (0.6-3.0) years.

Main Outcome and Measures

Segregation, measured using the Theil H method to calculate segregation tertiles in zip code tabulation areas based on the American Community Survey 5-year estimates, reflects the heterogeneity in neighborhood racial and ethnic composition. To quantify the likelihood of LDKT by neighborhood segregation, cause-specific hazard models were adjusted for individual-level and neighborhood-level factors and included an interaction between segregation tertiles and race.

Results

Among 162 587 candidates for kidney transplant, the mean (SD) age was 51.6 (13.2) years, 65 141 (40.1%) were female, 80 023 (49.2%) were Black, and 82 564 (50.8%) were White. Among Black candidates, living in a high-segregation neighborhood was associated with 10% (adjusted hazard ratio [AHR], 0.90 [95% CI, 0.84-0.97]) lower access to LDKT relative to residence in low-segregation neighborhoods; no such association was observed among White candidates (P for interaction = .01). Both Black candidates (AHR, 0.94 [95% CI, 0.89-1.00]) and White candidates (AHR, 0.92 [95% CI, 0.88-0.97]) listed at transplant centers in high-segregation neighborhoods had lower access to LDKT relative to their counterparts listed at centers in low-segregation neighborhoods (P for interaction = .64). Within high-segregation transplant center neighborhoods, candidates listed at predominantly minority neighborhoods had 17% lower access to LDKT relative to candidates listed at predominantly White neighborhoods (AHR, 0.83 [95% CI, 0.75-0.92]). Black candidates residing in or listed at transplant centers in predominantly minority neighborhoods had significantly lower likelihood of LDKT relative to White candidates residing in or listed at transplant centers located in predominantly White neighborhoods (65% and 64%, respectively).

Conclusions

Segregated residential and transplant center neighborhoods likely serve as a mechanism of structural racism, contributing to persistent racial disparities in access to LDKT. To promote equitable access, studies should assess targeted interventions (eg, community outreach clinics) to improve support for potential candidates and donors and ultimately mitigate the effects of segregation.

[The German Transplant Registry - An Analysis of Legacy Data 2006-2016]

INTRODUCTION

In 2018, medical transplant data from three institutions were merged to create a German transplant registry. Since June 2021, access to data of the registry has been available. It was planned to analyze the registry data in order to compare special allocation rules with regular allocation for heart, liver, lung, and kidney transplantation. Our approach led to a quality analysis of the registry.

METHODS

Upon request, legacy data (2006-2016) of the registry was provided, divided into 61 elements. From these elements, the user had to compile the required dataset. Data checks were performed for completeness, correct allocation of information, and consistency among different sources. Software used for these tasks included R, SQL, and Excel.

RESULTS

The initial elements ("waiting list" elements) of the four types of transplantations contained data from a total of 80,259 originally listed patients. However, these patients were only partially present in other elements resulting in complete datasets reflecting waiting time in only 23%, 30%, 50%, and 96%, and for post-transplantation outcomes in 14%, 11%, 38%, and 13% (heart, liver, lung, and kidney transplantation, respectively). The linking of urgency information with clinical data was successful in only a small proportion, with only 6% for heart transplantation. Incorrect and thus implausible allocations in the case of special allocation rules indicated incorrect entries in the registry. Data from different data providers were inconsistent.

DISCUSSION

The incompleteness and incorrect data allocation raise doubts about the reliability of scientific studies based on the transplant registry. The complex structure also hinders the compilation of a reliable dataset, which is uncommon internationally. New data (acquisition since 2017) has only been available since December 2023.

CONCLUSION

The transplant registry urgently needs restructuring. Competent clinical data management, involving transplant medical expertise, and continuous quality controls are essential in this process.

Single center utilization and post-transplant outcomes of thoracoabdominal normothermic regional perfusion deceased cardiac donor organs

INTRODUCTION

Thoracoabdominal normothermic regional perfusion (TA-NRP) following cardiac death is an emerging multivisceral organ procurement technique. Recent national studies on outcomes of presumptive TA-NRP-procured organs are limited by potential misclassification since TA-NRP is not differentiated from donation after cardiac death (DCD) in registry data.

METHODS

We studied 22 donors whose designees consented to TA-NRP and organ procurement performed at our institution between January 20, 2020 and July 3, 2022. We identified these donors in SRTR to describe organ utilization and recipient outcomes and compared them to recipients of traditional DCD (tDCD) and donation after brain death (DBD) organs during the same timeframe.

RESULTS

All 22 donors progressed to cardiac arrest and underwent TA-NRP followed by heart, lung, kidney, and/or liver procurement. Median donor age was 41 years, 55% had anoxic brain injury, 45% were hypertensive, 0% were diabetic, and median kidney donor profile index was 40%. TA-NRP utilization was high across all organ types (88%-100%), with a higher percentage of kidneys procured via TA-NRP compared to tDCD (88% vs. 72%, p = .02). Recipient and graft survival ranged from 89% to 100% and were comparable to tDCD and DBD recipients (p ≥ .2). Delayed graft function was lower for kidneys procured from TA-NRP compared to tDCD donors (27% vs. 44%, p = .045).

CONCLUSION

Procurement from TA-NRP donors yielded high organ utilization, with outcomes comparable to tDCD and DBD recipients across organ types. Further large-scale study of TA-NRP donors, facilitated by its capture in the national registry, will be critical to fully understand its impact as an organ procurement technique.

Wait Time Advantage for Transplant Candidates With HIV Who Accept Kidneys From Donors With HIV Under the HOPE Act

BACKGROUND

Kidney transplant (KT) candidates with HIV face higher mortality on the waitlist compared with candidates without HIV. Because the HIV Organ Policy Equity (HOPE) Act has expanded the donor pool to allow donors with HIV (D + ), it is crucial to understand whether this has impacted transplant rates for this population.

METHODS

Using a linkage between the HOPE in Action trial (NCT03500315) and Scientific Registry of Transplant Recipients, we identified 324 candidates listed for D + kidneys (HOPE) compared with 46 025 candidates not listed for D + kidneys (non-HOPE) at the same centers between April 26, 2018, and May 24, 2022. We characterized KT rate, KT type (D + , false-positive [FP; donor with false-positive HIV testing], D - [donor without HIV], living donor [LD]) and quantified the association between HOPE enrollment and KT rate using multivariable Cox regression with center-level clustering; HOPE was a time-varying exposure.

RESULTS

HOPE candidates were more likely male individuals (79% versus 62%), Black (73% versus 35%), and publicly insured (71% versus 52%; P  < 0.001). Within 4.5 y, 70% of HOPE candidates received a KT (41% D + , 34% D - , 20% FP, 4% LD) versus 43% of non-HOPE candidates (74% D - , 26% LD). Conversely, 22% of HOPE candidates versus 39% of non-HOPE candidates died or were removed from the waitlist. Median KT wait time was 10.3 mo for HOPE versus 60.8 mo for non-HOPE candidates ( P  < 0.001). After adjustment, HOPE candidates had a 3.30-fold higher KT rate (adjusted hazard ratio = 3.30, 95% confidence interval, 2.14-5.10; P  < 0.001).

CONCLUSIONS

Listing for D + kidneys within HOPE trials was associated with a higher KT rate and shorter wait time, supporting the expansion of this practice for candidates with HIV.

Racial Disparities in Waiting List Outcomes of Patients Listed for Lung Transplantation

BACKGROUND

The Lung Allocation Score, implemented in 2005, prioritized lung transplant candidates by medical urgency rather than waiting list time and was expected to improve racial disparities in transplant allocation. We evaluated whether racial disparities in lung transplant persisted after 2005.

METHODS

We identified all wait-listed adult lung transplant candidates in the United States from 2005 through 2021 using the Scientific Registry of Transplant Recipients. We evaluated the association between race and receipt of a transplant by using a multivariable competing risk regression model adjusted for demographics, socioeconomic status, Lung Allocation Score, clinical measures, and time. We evaluated interactions between race and age, sex, socioeconomic status, and Lung Allocation Score.

RESULTS

We identified 33,158 candidates on the lung transplant waiting list between 2005 and 2021: 27,074 White (82%), 3350 African American (10%), and 2734 Hispanic (8%). White candidates were older, had higher education levels, and had lower Lung Allocation Scores (P < .001). After multivariable adjustment, African American and Hispanic candidates were less likely to receive lung transplants than White candidates (African American: adjusted subhazard ratio, 0.86; 95% CI, 0.82-0.91; Hispanic: adjusted subhazard ratio, 0.82; 95% CI, 0.78-0.87). Lung transplant was significantly less common among Hispanic candidates aged >65 years (P = .003) and non-White candidates from higher-poverty communities (African-American: P = .013; Hispanic: P =.0036).

CONCLUSIONS

Despite implementation of the Lung Allocation Score, racial disparities persisted for wait-listed African American and Hispanic lung transplant candidates and differed by age and poverty status. Targeted interventions are needed to ensure equitable access to this life-saving intervention.

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.

Unrecognized opportunities: The landscape of pediatric kidney-paired donation in the United States

BACKGROUND

Pediatric (age < 18 years) kidney transplant (KT) candidates face increasingly complex choices. The 2014 kidney allocation system nearly doubled wait times for pediatric recipients. Given longer wait times and new ways to optimize compatibility, more pediatric candidates may consider kidney-paired donation (KPD). Motivated by this shift and the potential impact of innovations in KPD practice, we studied pediatric KPD procedures in the US from 2008 to 2021.

METHODS

We describe the characteristics and outcomes of pediatric KPD recipients with comparison to pediatric non-KPD living donor kidney transplants (LDKT), pediatric LDKT recipients, and pediatric deceased donor (DDKT) recipients.

RESULTS

Our study cohort includes 4987 pediatric DDKTs, 3447 pediatric non-KPD LDKTs, and 258 pediatric KPD transplants. Fewer centers conducted at least one pediatric KPD procedure compared to those that conducted at least one pediatric LDKT or DDKT procedure (67, 136, and 155 centers, respectively). Five centers performed 31% of the pediatric KPD transplants. After adjustment, there were no differences in graft failure or mortality comparing KPD recipients to non-KPD LDKT, LDKT, or DDKT recipients.

DISCUSSION

We did not observe differences in transplant outcomes comparing pediatric KPD recipients to controls. Considering these results, KPD may be underutilized for pediatric recipients. Pediatric KT centers should consider including KPD in KT candidate education. Further research will be necessary to develop tools that could aid clinicians and families considering the time horizon for future KT procedures, candidate disease and histocompatibility characteristics, and other factors including logistics and donor protections.

Uptake and 1-year outcomes of lung transplantation for COVID-19

OBJECTIVE

End-stage lung disease from severe COVID-19 infection is an increasingly common indication for lung transplantation (LT), but there are limited data on outcomes. We evaluated 1-year COVID-19 LT outcomes.

METHODS

We identified all adult US LT recipients January 2020 to October 2022 in the Scientific Registry for Transplant Recipients, using diagnosis codes to identify recipients transplanted for COVID-19. We used multivariable regression to compare in-hospital acute rejection, prolonged ventilator support, tracheostomy, dialysis, and 1-year mortality between COVID-19 and non-COVID-19 recipients, adjusting for donor, recipient, and transplant characteristics.

RESULTS

LT for COVID-19 increased from 0.8% to 10.7% of total LT volume during 2020 to 2021. The number of centers performing LT for COVID-19 increased from 12 to 50. Recipients transplanted for COVID-19 were younger; were more likely to be male and Hispanic; were more likely to be on a ventilator, extracorporeal membrane oxygenation support, and dialysis pre-LT; were more likely to receive bilateral LT; and had higher lung allocation score and shorter waitlist time than other recipients (all P values < .001). COVID-19 LT had higher risk of prolonged ventilator support (adjusted odds ratio, 2.28; P < .001), tracheostomy (adjusted odds ratio 5.3; P < .001), and longer length of stay (median, 27 vs 19 days; P < .001). Risk of in-hospital acute rejection (adjusted odds ratio, 0.99; P = .95) and 1-year mortality (adjusted hazard ratio, 0.73; P = .12) were similar for COVID-19 LTs and LTs for other indications, even accounting for center-level differences.

CONCLUSIONS

COVID-19 LT is associated with higher risk of immediate postoperative complications but similar risk of 1-year mortality despite more severe pre-LT illness. These encouraging results support the ongoing use of LT for COVID-19-related lung disease.

Multi-Task Learning for Post-transplant Cause of Death Analysis: A Case Study on Liver Transplant

Organ transplant is the essential treatment method for some end-stage diseases, such as liver failure. Analyzing the post-transplant cause of death (CoD) after organ transplant provides a powerful tool for clinical decision making, including personalized treatment and organ allocation. However, traditional methods like Model for End-stage Liver Disease (MELD) score and conventional machine learning (ML) methods are limited in CoD analysis due to two major data and model-related challenges. To address this, we propose a novel framework called CoD-MTL leveraging multi-task learning to model the semantic relationships between various CoD prediction tasks jointly. Specifically, we develop a novel tree distillation strategy for multi-task learning, which combines the strength of both the tree model and multi-task learning. Experimental results are presented to show the precise and reliable CoD predictions of our framework. A case study is conducted to demonstrate the clinical importance of our method in the liver transplant.

COVID-19 and Access to Kidney Transplantation for Older Candidates in the United States: A National Registry Study

Rationale & Objective

Coronavirus disease (COVID)-19 has likely impacted accessibility to transplantation services among older adults (age ≥65 years). We quantified the impact of COVID-19 on kidney transplantation access for older kidney-only candidates registered on the United States (US) kidney waitlist.

Study Design

Retrospective analysis of registry data.

Setting & Participants

57,222 older adults who were part of or added to the US kidney waitlist between January 1, 2016 and February 28, 2022, identified using the Scientific Registry of Transplant Recipients (SRTR).

Exposures

Four COVID-19 waves and one nonwave period based on the national incidence of COVID-19 in the US (initial: March 15-May 30, 2020; winter 2020-2021: December 1, 2020-January 31, 2021; delta: August 1, 2021-September 30, 2021; omicron: December 1, 2021-February 28, 2022; nonwave: inter-wave periods).

Outcomes

Waitlist registrations, deceased-donor kidney transplants, living-donor kidney transplants, waitlist mortality, and waitlist removals due to deteriorating condition (hereafter referred to as removals).

Analytical Approach

Poisson regression for the adjusted incidence rate ratio (aIRR) of each outcome during the COVID-19 waves and the nonwave period relative to reference (January 1, 2016-December 31, 2019), adjusted for seasonality and secular trends.

Results

Waitlist registrations initially declined and increased henceforth. Deceased-donor kidney transplants and living-donor kidney transplants remained below-expected levels during all waves. Waitlist mortality peaked during the winter 2020-2021 wave (aIRR: 1.701.982.30) and has declined since; mortality rates were 139%, 107%, and 251% above expected for Black candidates, men, and candidates aged ≥75 years, respectively, during the winter 2020-2021 wave. Removals increased from 22% below expected levels (initial wave) to 26% above expected levels (omicron wave); removals were nonsignificantly higher than expected during the omicron wave for older Black and Hispanic candidates.

Limitations

The findings are not generalizable to those listed at earlier ages with prolonged waitlist times. Additionally, using national COVID-19 incidence does not consider local policy and health care variations. Lastly, aIRRs must be interpreted cautiously due to smaller daily event counts.

Conclusions

COVID-19 was associated with fewer transplants and increased mortality and removals in older kidney transplant candidates. Transplant providers should consider this impact and implement policies and practices to ensure the continuity of care.

Plain-Language Summary

The proportion of older adults on the kidney transplant waitlist is increasing, but the impact of COVID-19 on this population is not well characterized. In this study, we looked at incident waitlist registrations, deceased- and living-donor kidney transplants, and waitlist mortality and removals due to deteriorating condition over 4 waves of COVID-19. We found that transplantation services did not fully recover to prepandemic levels as of March 2022. Notably, racial/ethnic minorities and older men experienced lower rates of kidney transplants and higher rates of waitlist mortality, respectively, relative to White candidates and older women. Identifying vulnerable subpopulations affected by COVID-19 and its long-term impact is crucial for creating strategies to ensure the continuity of care in this population during public health emergencies.

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.

Evaluating Cost-Effectiveness in Using High-Kidney Donor Profile Index Organs

A more granular donor kidney grading scale, the kidney donor profile index (KDPI), has recently emerged in contradistinction to the standard criteria donor/expanded criteria donor framework. In this paper, we built a Markov decision process model to evaluate the survival, quality-adjusted life years (QALY), and cost advantages of using high-KDPI kidneys based on multiple KDPI strata over a 60-month time horizon as opposed to remaining on the waiting list waiting for a lower-KDPI kidney. Data for the model were gathered from the Scientific Registry of Transplant Recipients and the United States Renal Data System Medicare parts A, B, and D databases. Of the 129,024 phenotypes delineated in this model, 65% of them would experience a survival benefit, 81% would experience an increase in QALYs, 87% would see cost-savings, and 76% would experience cost-savings per QALY from accepting a high-KDPI kidney rather than remaining on the waiting list waiting for a kidney of lower-KDPI. Classification and regression tree analysis (CART) revealed the main drivers of increased survival in accepting high-KDPI kidneys were wait time ≥30 months, panel reactive antibody (PRA) <90, age ≥45 to 65, diagnosis leading to renal failure, and prior transplantation. The CART analysis showed the main drivers of increased QALYs in accepting high-kidneys were wait time ≥30 months, PRA <90, and age ≥55 to 65.

Thoracic retransplantation: Does time to retransplantation matter?

OBJECTIVE

For some individuals, chronic allograft failure is best treated with retransplantation. We sought to determine if time to retransplantation impacts short- and long-term outcomes for heart or lung retransplant recipients with a time to retransplantation more than 1 year.

METHODS

The United Network for Organ Sharing/Organ Procurement and Transplantation Network STAR file was queried for all adult, first-time heart (June 1, 2006, to September 30, 2020) and lung (May 1, 2005, to September 30, 2020) retransplantations with a time to retransplantation of at least 1 year. Patients were grouped according to the tertile of time to retransplantation (tertile 1: 1-7.7 years, tertile 2: 7.7-14.7 years, tertile 3: 14.7+ years; lung: tertile 1: 1-2.8 years, tertile 2: 2.8-5.6 years, tertile 3: 5.6+ years). The primary outcome was survival after retransplantation. Comparative statistics identified differences in groups, and Kaplan-Meier methods and a Cox proportional hazard model were used for survival analysis.

RESULTS

After selection, 908 heart and 871 lung retransplants were identified. Among heart retransplant recipients, tertile 1 was associated with male sex, smoking history, higher listing status, and increased mechanical support pretransplant. Tertile 3 had the highest rate of concomitant kidney transplant; however, the incidence of morbidity and in-hospital mortality was similar among the groups. Unadjusted and adjusted analyses revealed no survival difference among all groups. Regarding lung retransplant recipients, tertile 1 was associated with increased lung allocation score, pretransplant hospitalization, and mechanical support. Unadjusted and adjusted survival analyses revealed decreased survival in tertile 1.

CONCLUSIONS

Time to retransplant does not appear to affect heart recipients with a time to retransplantation of more than 1 year; however, shorter time to retransplantation for prior lung recipients is associated with decreased survival. Potential lung retransplant candidates with a time to retransplantation of less than 2.8 years should be carefully evaluated before retransplantation.

The causes of death in patients with nonalcoholic steatohepatitis following liver transplantation stratified using pre-liver transplant BMI

BACKGROUND & AIMS

Determining the effects of pre-liver transplant (LT) BMI independent of underlying ascites on the post-LT outcomes of patients with nonalcoholic steatohepatitis (NASH) is needed to clarify the paradoxical and protective effects of obesity on post-LT endpoints. In order to accomplish this, we used graded severities of ascites to stratify the NASH-LT population and to perform an ascites-specific strata analysis with differing pre-LT BMI levels.

METHODS

2005-2019 United Network for Organ Sharing (UNOS) Standard Transplant Analysis and Research (STAR) database was queried to select patients with NASH, who were categorized into specific sets of ascites severity: no ascites (n = 1188), mild ascites (n = 4463), and moderate ascites (n = 3525). Then, BMI classification (underweight: < 18.5, normal: 18.5-25, overweight: 25-30, obese: ≥ 30 kg/m2) was used to stratify each ascites-specific group and to compare to the post-LT mortality endpoints. Those under 18 years old and those who received living/multi-organ transplants were excluded.

RESULTS

Among each ascites category, there were the following numbers of normal, underweight, overweight, and obese BMI patients respectively; no ascites: 161, 4, 359, 664; mild ascites: 643, 28, 1311, 2481; and moderate ascites: 529, 25, 1030, 1941. The obese BMI cohort was at a lower risk of all-cause mortality compared to recipients with normal BMI with mild ascites (aHR: 0.79, 95% Confidence Interval (CI) 0.65-0.94, p-value = 0.010; case-incidence 47.10 vs 56.81 deaths per 1000 person-years) and moderate ascites (aHR: 0.77, 95% CI 0.63-0.94, p-value = 0.009; case-incidence 53.71 vs 66.17 deaths per 1000 person-years). In addition, the overweight BMI cohort with mild ascites demonstrated a lower hazard of all-cause mortality (aHR: 0.80, 95% CI 0.66-0.97, p-value = 0.03; case-incidence 49.09 vs 56.81 deaths per 1000 person-years). There was no difference in graft failure for the three BMI groups (underweight, overweight, and obese) in comparison to normal BMI. Furthermore, the overweight BMI group with mild ascites cohort demonstrated a lower hazard of death due to general infectious causes (aHR: 0.51, 95% CI 0.32-0.83, p = 0.006; case-incidence 6.12 vs 11.91 deaths per 1000 person-years) and sepsis (aHR: 0.49, 95% CI 0.27-0.86, p = 0.01; case-incidence 4.31 vs 8.50 deaths per 1000 person-years).

CONCLUSION

The paradoxical effects of obesity in reducing the risks of all-cause death appears to be in part modulated by ascites. The current study emphasizes the need to evaluate BMI with concomitant ascites severity pre-LT to accurately prognosticate post-LT outcomes when evaluating NASH patients with advanced liver disease.

Transplant Candidate Outcomes After Declining a DCD Liver in the United States

BACKGROUND

In the context of the organ shortage, donation after circulatory death (DCD) provides an opportunity to expand the donor pool. Although deceased-donor liver transplantation from DCD donors has expanded, DCD livers continue to be discarded at elevated rates; the use of DCD livers from older donors, or donors with comorbidities, is controversial.

METHODS

Using US registry data from 2009 to 2020, we identified 1564 candidates on whose behalf a DCD liver offer was accepted ("acceptors") and 16 981 candidates on whose behalf the same DCD offers were declined ("decliners"). We characterized outcomes of decliners using a competing risk framework and estimated the survival benefit (adjusted hazard ratio [95% confidence interval]) of accepting DCD livers using Cox regression.

RESULTS

Within 10 y of DCD offer decline, 50.9% of candidates died or were removed from the waitlist before transplantation with any type of allograft. DCD acceptors had lower mortality compared with decliners at 10 y postoffer (35.4% versus 48.9%, P < 0.001). After adjustment for candidate covariates, DCD offer acceptance was associated with a 46% reduction in mortality (0.54 [0.49-0.61]). Acceptors of older (age ≥50), obese (body mass index ≥30), hypertensive, nonlocal, diabetic, and increased risk DCD livers had 44% (0.56 [0.42-0.73]), 40% (0.60 [0.49-0.74]), 48% (0.52 [0.41-0.66]), 46% (0.54 [0.45-0.65]), 32% (0.68 [0.43-1.05]), and 45% (0.55 [0.42-0.72]) lower mortality risk compared with DCD decliners, respectively.

CONCLUSIONS

DCD offer acceptance is associated with considerable long-term survival benefits for liver transplant candidates, even with older DCD donors or donors with comorbidities. Increased recovery and utilization of DCD livers should be encouraged.

Characterizing the risk of human leukocyte antigen-incompatible living donor kidney transplantation in older recipients

Older compatible living donor kidney transplant (CLDKT) recipients have higher mortality and death-censored graft failure (DCGF) compared to younger recipients. These risks may be amplified in older incompatible living donor kidney transplant (ILDKT) recipients who undergo desensitization and intense immunosuppression. In a 25-center cohort of ILDKT recipients transplanted between September 24, 1997, and December 15, 2016, we compared mortality, DCGF, delayed graft function (DGF), acute rejection (AR), and length of stay (LOS) between 234 older (age ≥60 years) and 1172 younger (age 18-59 years) recipients. To investigate whether the impact of age was different for ILDKT recipients compared to 17 542 CLDKT recipients, we used an interaction term to determine whether the relationship between posttransplant outcomes and transplant type (ILDKT vs CLDKT) was modified by age. Overall, older recipients had higher mortality (hazard ratio: 1.632.072.65, P < .001), lower DCGF (hazard ratio: 0.360.530.77, P = .001), and AR (odds ratio: 0.390.540.74, P < .001), and similar DGF (odds ratio: 0.461.032.33, P = .9) and LOS (incidence rate ratio: 0.880.981.10, P = 0.8) compared to younger recipients. The impact of age on mortality (interaction P = .052), DCGF (interaction P = .7), AR interaction P = .2), DGF (interaction P = .9), and LOS (interaction P = .5) were similar in ILDKT and CLDKT recipients. Age alone should not preclude eligibility for ILDKT.

Transplanting candidates with stacked risks negatively affects outcomes

BACKGROUND

Lung transplant (LT) centers are increasingly evaluating patients with multiple risk factors for adverse outcomes. The effects of these stacked risks remains unclear. Our aim was to determine the relationship between the number of comorbidities and post-transplant outcomes.

METHODS

We performed a retrospective cohort study using the National Inpatient Sample (NIS) and UNOS Starfile (USF). We applied a probabilistic matching algorithm using 7 variables (transplant: month, year, and type; recipient: age, sex, race, payer). We matched recipients in the USF to transplant patients in the NIS between 2016 and 2019. The Elixhauser methodology was used to identify comorbidities present on admission. We determined the associations between mortality, length of stay (LOS), total charges, and disposition with comorbidity numbers using penalized cubic splines, Kaplan-Meier, and linear and logistic regression methods.

RESULTS

From 28,484,087 NIS admissions, we identified 1,821 LT recipients. Matches were exact in 76.8% of the cohort. While the remaining cohort had a probability match of ≥0.94. Penalized splines of Elixhauser comorbidity number identified 3 knots defining 3 groups of stacked risk: low (<3), medium (3-6), and high risk (>6). Inpatient mortality increased from low to medium to high-risk categories: (1.6%, 3.9%, and 7.0%; p < 0.001), as did LOS (16, 21, 29 days, p < 0.001), total charges ($553,057, $666,791, $821,641.5; p = 0.004) and discharge to a skilled nursing facility (15%, 20%, 31%; p < 0.001).

CONCLUSIONS

Stacked risks adversely affect post-LT mortality, LOS, charges, and discharge disposition. Further study to understand the details of specific stacked risks is warranted.

External Validation of Toulouse-Rangueil eGFR12 Prediction Model After Living Donor Nephrectomy

Decreased postdonation eGFR is associated with a higher risk of ESRD after living kidney donation, even when accounting for predonation characteristics. The Toulouse-Rangueil model (TRM) estimates 12 month postdonation eGFR (eGFR12) to inform counseling of candidates for living donation. The TRM was validated in several single-center European cohorts but has not been validated in US donors. We assessed the TRM in living kidney donors in the US using SRTR data 1/2000-6/2021. We compared the 2021 CKD-EPI equation eGFR12 observed estimates to the TRM eGFR12 predictions. Median (IQR) bias was -3.4 (-9.3, 3.4) mL/min/1.73 m2. Bias was higher for males vs. females (bias [IQR] -4.4 [-9.9, 1.8] vs. -2.9 [-8.8, 4.1]) and younger (31-40) vs. older donors (>50) (bias -4.9 [-10.6, 3.0] vs. -2.1 [-7.5, 4.0]). Bias was also larger for Black vs. White donors (bias (-6.7 [-12.1, -0.3], p < 0.001) vs. (-3.4 [-9.1, 3.1], p < 0.001)). Overall correlation was 0.71. In a sensitivity analysis using the 2009 CKD-EPI equation, results were generally consistent with exception to a higher overall bias (bias -4.2 [-9.8, 2.4]). The TRM overestimates postdonation renal function among US donors. Overestimation was greatest for those at higher risk for postdonation ESRD including male, Black, and younger donors. A new equation is needed to estimate postdonation renal function.

Removing geographic boundaries from liver allocation: A method for designing continuous distribution scores

BACKGROUND

The Organ Procurement and Transplantation Network (OPTN) is eliminating geographic boundaries in liver allocation, in favor of continuous distribution. Continuous distribution allocates organs via a composite allocation score (CAS): a weighted sum of attributes like medical urgency, candidate biology, and placement efficiency. The opportunity this change represents, to include new variables and features for prioritizing candidates, will require lengthy and contentious discussions to establish community consensus. Continuous distribution could instead be implemented rapidly by computationally translating the allocation priorities for pediatric, status 1, and O/B blood type liver candidates that are presently implemented via geographic boundaries into points and weights in a CAS.

METHODS

Using simulation with optimization, we designed a CAS that is minimally disruptive to existing prioritizations, and that eliminates geographic boundaries and minimizes waitlist deaths without harming vulnerable populations.

RESULTS

Compared with Acuity Circles (AC) in a 3-year simulation, our optimized CAS decreased deaths from 7771.2 to 7678.8 while decreasing average (272.66 NM vs. 264.30 NM) and median (201.14 NM vs. 186.49 NM) travel distances. Our CAS increased travel only for high MELD and status 1 candidates (423.24 NM vs. 298.74 NM), and reduced travel for other candidates (198.98 NM vs. 250.09 NM); overall travel burden decreased.

CONCLUSION

Our CAS reduced waitlist deaths by sending livers for high-MELD and status 1 candidates farther, while keeping livers for lower MELD candidates nearby. This advanced computational method can be applied again after wider discussions of adding new priorities conclude; our method designs score weightings to achieve any specified feasible allocation outcomes.

The impact of recipient and donor gender-match and mismatch on the post-liver transplant outcomes of patients with primary biliary cholangitis

BACKGROUND & AIMS

In this study, we evaluate the effects of donor gender on post-liver transplant (LT) prognosis. We specifically consider patients with primary biliary cholangitis (PBC).

METHODS

The 2005 to 2019 UNOS transplant registry was used to select patients with PBC. The study cohort was stratified by donor gender. All-cause mortality and graft failure hazards were compared using iterative Cox regression analysis. Subanalyses were performed to evaluate gender mismatch on post-LT prognosis.

RESULTS

There were 1885 patients with PBC. Of these cases, 965 entries had male donors and 920 had female donors. Median follow-up was 4.82 (25-75% IQR 1.83-8.93) years. Having a male donor was associated with higher all-cause mortality (aHR 1.28 95%CI 1.03-1.58) and graft failure (aHR 1.70 95%CI 1.02-2.82). Corresponding incidence rates were also relatively increased. In the sub-analysis of female recipients (n = 1581), those with gender-mismatch (male donors, n = 769) were associated with higher all-cause mortality (aHR 1.41 95%CI 1.11-1.78) but not graft failure. In the male recipient subanalysis (n = 304), no associations were found between gender-mismatch (female donors, n = 108) and all-cause mortality or graft failure.

CONCLUSION

This study shows that recipients who have male donors experienced higher rates of all-cause mortality following LT. This finding was consistent in the female recipient-male donor mismatch cohort.

Identifying predictors of resilience to stressors in single-arm studies of pre-post change

Many older adults experience a major stressor at some point in their lives. The ability to recover well after a major stressor is known as resilience. An important goal of geriatric research is to identify factors that influence resilience to stressors. Studies of resilience in older adults are typically conducted with a single-arm where everyone experiences the stressor. The simplistic approach of regressing change versus baseline yields biased estimates due to mathematical coupling and regression to the mean (RTM). We develop a method to correct the bias. We extend the method to include covariates. Our approach considers a counterfactual control group and involves sensitivity analyses to evaluate different settings of control group parameters. Only minimal distributional assumptions are required. Simulation studies demonstrate the validity of the method. We illustrate the method using a large, registry of older adults (N  =7239) who underwent total knee replacement (TKR). We demonstrate how external data can be utilized to constrain the sensitivity analysis. Naive analyses implicated several treatment effect modifiers including baseline function, age, body-mass index (BMI), gender, number of comorbidities, income, and race. Corrected analysis revealed that baseline (pre-stressor) function was not strongly linked to recovery after TKR and among the covariates, only age and number of comorbidities were consistently and negatively associated with post-stressor recovery in all functional domains. Correction of mathematical coupling and RTM is necessary for drawing valid inferences regarding the effect of covariates and baseline status on pre-post change. Our method provides a simple estimator to this end.

Outcomes of COVID-19-Positive Donor Heart Transplantation in the United States

Background Little is known regarding the impact of donor COVID-19 status on recipient outcomes after heart transplantation. In this study, we characterize outcomes of the first 110 heart transplants from organ donors positive for COVID-19 (COVID-19+) in the United States. Methods and Results Retrospective analysis of the United Network for Organ Sharing database was performed for single-organ adult heart transplants from January 2020 to March 2022. Donor COVID-19+ status was defined as a positive nucleic acid amplification, antigen, or other COVID-19 test within 7 days of transplant. Nearest-neighbor propensity score matching used to adjust for differences between recipients of COVID-19+ and nonpositive donor hearts. Overall, 7251 heart transplants were included in analysis, with 110 using COVID-19+ donor hearts. Recipients of COVID-19+ allografts were younger (54 [interquartile range, 41-61]) versus 57 [46-64] years; P=0.02) but had similar rates of female sex and non-White race compared with those receiving allografts from negative donors. Nearest-neighbor propensity score matching resulted in 100 well-matched pairs of recipients of COVID-19+ versus nonpositive donor organs. The 2 matched groups had similar median lengths of stay (15 [11-23] days versus 15 [13-23] days; P=0.40), rates of graft failure (1% versus 0%; P=0.99), 30-day death (3% versus 3%; P=0.99), and 3-month survival (88% versus 94%; P=0.23) compared with recipients of nonpositive donors. No deaths occurred due to COVID-19 infection among the 8 (7%) total deceased recipients of COVID-19+ allografts to date. Conclusions Short-term outcomes of heart transplant recipients receiving COVID-19+ donor organs are reassuring. However, continued monitoring for long-term survival and potential complications are warranted.

Excess mortality after kidney transplantation: does sex matter?

Understanding sex differences in graft outcomes within the course of kidney transplantation is needed to unravel factors leading to the observed disparities and further improve patient management. In this issue, Vinson et al. presented a relative survival analysis comparing the excess risk of mortality in female and male recipients after kidney transplantation. This commentary discusses the major findings but also the challenges of the use of registry data to conduct large-scale analyses.

Statins in Kidney Transplant Recipients: Usage, All-Cause Mortality, and Interactions with Maintenance Immunosuppressive Agents

SIGNIFICANCE STATEMENT

Cardiovascular diseases account for 32% of deaths among kidney transplant recipients. Statin therapy is common in this population. However, its effect on mortality prevention remains unclear among kidney transplant recipients, whose clinical risk profile might be unique because of concomitant immunosuppressive therapy. In this national study of 58,264 single-kidney transplant recipients, statin use was associated with a 5% decrease in mortality. More importantly, this protective association was stronger among those who used a mammalian target of rapamycin (mTOR) inhibitor for immunosuppression (27% decrease in mTOR inhibitor users versus 5% in nonusers). Our results suggest that statin therapy may reduce mortality in kidney transplant recipients and that the strength of this protective association may vary by immunosuppression regimen.

BACKGROUND

Cardiovascular diseases are the leading cause of mortality in kidney transplant (KT) recipients, accounting for 32% of deaths. Statins are widely used in KT recipients, but effectiveness for preventing mortality remains unclear in this population, especially because of interaction between statins and immunosuppressive agents. We analyzed a national cohort to assess the real-world effectiveness of statins for reducing all-cause mortality in KT recipients.

METHODS

We studied statin use and mortality among 58,264 adults (18 years or older) who received single kidneys between 2006 and 2016 and had Medicare part A/B/D. Statin use was ascertained from Medicare prescription drug claims and deaths from Center for Medicare and Medicaid Services records. We estimated the association of statin use with mortality using multivariable Cox models, with statin use as a time-varying exposure and immunosuppression regimen as effect modifiers.

RESULTS

Statin use increased from 45.5% at KT to 58.2% at 1-year post-KT to 70.9% at 5-year post-KT. We observed 9785 deaths over 236,944 person-years. Overall, statin use was significantly associated with lower mortality (adjusted hazard ratio [aHR], 0.95; 95% confidence interval [CI], 0.90 to 0.99). The strength of this protective association varied by calcineurin inhibitor use (among tacrolimus users, aHR, 0.97; 95% CI, 0.92 to 1.03 versus among calcineurin nonusers, aHR, 0.72; 95% CI, 0.60 to 0.87; interaction P =0.002), mammalian target of rapamycin (mTOR) inhibitor use (among mTOR inhibitor users, aHR, 0.73; 95% CI, 0.57 to 0.92 versus among nonusers, aHR, 0.95; 95% CI, 0.91 to 1.00; interaction P =0.03), and mycophenolate use (among mycophenolate users, aHR, 0.96; 95% CI, 0.91 to 1.02 versus among nonusers, aHR, 0.76; 95% CI, 0.64 to 0.89; interaction P =0.002).

CONCLUSION

Real-world evidence supports statin therapy for reducing all-cause mortality in KT recipients. Effectiveness might be greater when combined with mTOR inhibitor-based immunosuppression.

Post-kidney transplant body mass index trajectories are associated with graft loss and mortality

BACKGROUND

Early post-kidney transplantation (KT) changes in physiology, medications, and health stressors likely impact body mass index (BMI) and likely impact all-cause graft loss and mortality.

METHODS

We estimated 5-year post-KT (n = 151 170; SRTR) BMI trajectories using an adjusted mixed effects model. We estimated long-term mortality and graft loss risks by 1-year BMI change quartile (decrease [1st quartile]: change < -.07 kg/m2 /month; stable [2nd quartile]: -.07 ≤ change ≤ .09 kg/m2 /month; increase [3rd, 4th quartile]: change > .09 kg/m2 /month) using adjusted Cox proportional hazards models.

RESULTS

BMI increased in the 3 years post-KT (.64 kg/m2 /year, 95% CI: .63, .64) and decreased in years 3-5 (-.24 kg/m2 /year, 95% CI: -.26, -.22). 1-year post-KT BMI decrease was associated with elevated risks of all-cause mortality (aHR = 1.13, 95% CI: 1.10-1.16), all-cause graft loss (aHR = 1.13, 95% CI: 1.10-1.15), death-censored graft loss (aHR = 1.15, 95% CI: 1.11-1.19), and mortality with functioning graft (aHR = 1.11, 95% CI: 1.08-1.14). Among recipients with obesity (pre-KT BMI≥30 kg/m2 ), BMI increase was associated with higher all-cause mortality (aHR = 1.09, 95% CI: 1.05-1.14), all-cause graft loss (aHR = 1.05, 95% CI: 1.01-1.09), and mortality with functioning graft (aHR = 1.10, 95% CI: 1.05-1.15) risks, but not death-censored graft loss risks, relative to stable weight. Among individuals without obesity, BMI increase was associated with lower all-cause graft loss (aHR = .97, 95% CI: .95-.99) and death-censored graft loss (aHR = .93, 95% CI: .90-.96) risks, but not all-cause mortality or mortality with functioning graft risks.

CONCLUSIONS

BMI increases in the 3 years post-KT, then decreases in years 3-5. BMI loss in all adult KT recipients and BMI gain in those with obesity should be carefully monitored post-KT.

The association of donor hepatitis C virus infection with 3-year kidney transplant outcomes in the era of direct-acting antiviral medications

To determine the effect of donor hepatitis C virus (HCV) infection on kidney transplant (KT) outcomes in the era of direct-acting antiviral (DAA) medications, we examined 68,087 HCV-negative KT recipients from a deceased donor between March 2015 and May 2021. A Cox regression analysis was used to estimate adjusted hazard ratios (aHRs) of KT failure, incorporating inverse probability of treatment weighting to control for patient selection to receive an HCV-positive kidney (either nucleic acid amplification test positive [NAT+, n = 2331] or antibody positive (Ab+)/NAT- [n = 1826]) based on recipient characteristics. Compared with kidney from HCV-negative donors, those from Ab+/NAT- (aHR = 0.91; 95% confidence interval [CI], 0.75-1.10) and HCV NAT+ (aHR = 0.89; 95% CI, 0.73-1.08) donors were not associated with an increased risk of KT failure over 3 years after transplant. Moreover, HCV NAT+ kidneys were associated with a higher 1-year estimated glomerular filtration (63.0 vs 61.0 mL/min/1.73 m2, P = .007) and lower risk of delayed graft function (aOR = 0.76; 95% CI, 0.68-0.84) compared with HCV-negative kidneys. Our findings suggest that donor HCV positivity is not associated with an elevated risk of graft failure. The inclusion of donor HCV status in the Kidney Donor Risk Index may no longer be appropriate in contemporary practice.

Trends in the survival benefit of repeat kidney transplantation over the past 3 decades

Repeat kidney transplantation (re-KT) is the preferred treatment for patients with graft failure. Changing allocation policies, widening the risk profile of recipients, and improving dialysis care may have altered the survival benefit of a re-KT. We characterized trends in re-KT survival benefit over 3 decades and tested whether it differed by age, race/ethnicity, sex, and panel reactive assay (PRA). By using the Scientific Registry of Transplant Recipient data, we identified 25 419 patients who underwent a re-KT from 1990 to 2019 and 25 419 waitlisted counterfactuals from the same year with the same waitlisted time following graft failure. In the adjusted analysis, a re-KT was associated with a lower risk of death (adjusted hazard ratio [aHR] = 0.63; 95% confidence interval [CI], 0.61-0.65). By using the 1990-1994 era as a reference (aHR = 0.77; 95% CI, 0.69-0.85), incremental improvements in the survival benefit were noted (1995-1999: aHR = 0.72; 95% CI, 0.67-0.78: 2000-2004: aHR = 0.59; 95% CI, 0.55-0.63: 2005-2009: aHR = 0.59; 95% CI, 0.56-0.63: 2010-2014: aHR = 0.57; 95% CI, 0.53-0.62: 2015-2019: aHR = 0.64; 95% CI, 0.57-0.73). The survival benefit of a re-KT was noted in both younger (age = 18-64 years: aHR = 0.63; 95% CI, 0.61-0.65) and older patients (age ≥65 years: aHR = 0.66; 95% CI, 0.58-0.74; Pinteraction = .45). Patients of all races/ethnicities demonstrated similar benefits with a re-KT. However, it varied by the sex of the recipient (female patients: aHR = 0.60; 95% CI, 0.56-0.63: male patients: aHR = 0.66; 95% CI, 0.63-0.68; Pinteraction = .004) and PRA (0-20: aHR = 0.69; 95% CI, 0.65-0.74: 21-80: aHR = 0.61; 95% CI, 0.57-0.66; Pinteraction = .02; >80: aHR = 0.57; 95% CI, 0.53-0.61; Pinteraction< .001). Our findings support the continued practice of a re-KT and efforts to overcome the medical, immunologic, and surgical challenges of a re-KT.

The unfinished journey toward transplant equity: an analysis of racial/ethnic disparities for children after the implementation of the Kidney Allocation System in 2014

BACKGROUND

Disparities in pediatric kidney transplantation (KT) result in reduced access and worse outcomes for minority children. We assessed the impact of recent systems changes on these disparities.

METHODS

This is a retrospective cohort study of pediatric patients utilizing data from the US Renal Data System (n = 7547) and Scientific Registry of Transplant Recipients (n = 6567 waitlisted and n = 6848 transplanted patients). We compared access to transplantation, time to deceased donor kidney transplant (DDKT), and allograft failure (ACGF) in the 5 years preceding implementation of the Kidney Allocation System (KAS) to the 5 years post-KAS implementation 2010-2014 vs. 2015-2019, respectively.

RESULTS

Compared to the pre-KAS era, post-KAS candidates were more likely to be pre-emptively listed (26.8% vs. 38.1%, p < 0.001), pre-emptively transplanted (23.8% vs. 28.0%, p < 0.001), and less likely to have private insurance (35.6% vs. 32.3%, p = 0.01), but these were not uniform across racial groups. Compared to white children, Black and Hispanic children had a lower likelihood of transplant listing within 2 years of first dialysis service (aHR 0.590.670.76 and 0.730.820.92, respectively) in the post-KAS era. Time to DDKT was comparable across all racial groups in the post-KAS era. Compared to white children, Black DDKT recipients have more 5-year ACGF (aHR 1.001.432.06 p = 0.05) while there was no difference in 3- or 5-year ACGF among LDKT recipients.

CONCLUSIONS

After KAS implementation, there is equity in time to DDKT. Pre-KAS increased hazard of ACGF among Black children has decreased in the post-KAS era; however, persistent disparities exist in time to transplant listing among Black and Hispanic children when compared to white children. A higher resolution version of the Graphical abstract is available as Supplementary information.

P32: a sex- and gender-sensitive model for evidence-based precision medicine: from knowledge generation to implementation in the field of kidney transplantation

Precision medicine emerged as a promising approach to identify suitable interventions for individual patients with a particular health concern and at various time points. Technology can enable the acquisition of increasing volumes of clinical and "omics" data at the individual and population levels and support advanced clinical decision making. However, to keep pace with evolving societal realities and developments, it is important to systematically include sex- and gender-specific considerations in the research process, from the acquisition of knowledge to implementation. Building on the foundations of evidence-based medicine and existing precision medicine frameworks, we propose a novel evidence-based precision medicine framework in the form of the P3²model, which considers individual sex-related (predictive [P1], preventive [P2], and personalized [P3] medicine) and gender-related (participatory [P4], psychosocial [P5], and percipient [P6] medicine) domains and their intersection with ethnicity, geography, and other demographic and social variables, in addition to population, community, and public dimensions (population-informed [P7], partnered with community [P8], and public-engaging [P9] medicine, respectively). Through its ability to contextualize and reflect on societal realities and developments, our model is expected to promote consideration of diversity, equity, and inclusion principles and, thus, enrich science, increase reproducibility of research, and ensure its social impact.

Big Data in Surgery

The emergence of Big Data has been facilitated by technological advancements in the processing, storage, and analysis of large quantities of data. Its strength is derived from its size, ease of access, and speed of analysis, and it has enabled surgeons to investigate areas of interest that traditional research models have historically been unable to address. In the future, Big Data will likely assist in the incorporation of more advanced technologies into surgical practice, including artificial intelligence and machine learning to realize the full potential of Big Data in Surgery.

Trends in use and three-year outcomes of hepatitis C virus-viremic donor lung transplants for hepatitis C virus-seronegative recipients

OBJECTIVE

The feasibility and 6-month outcome safety of lung transplants (LTs) from hepatitis C virus (HCV)-viremic donors for HCV-seronegative recipients (R-) were established in 2019, but longer-term safety and uptake of this practice nationally remain unknown.

METHODS

We identified HCV-seronegative LT recipients (R-) 2015-2020 using the Scientific Registry of Transplant Recipients. We classified donors as seronegative (D-) or viremic (D+). We used χ2 testing, rank-sum testing, and Cox regression to compare posttransplant outcomes between HCV D+/R- and D-/R- LT recipients.

RESULTS

HCV D+/R- LT increased from 2 to 97/year; centers performing HCV D+/R- LT increased from 1 to 25. HCV D+/R- versus HCV D-/R- LT recipients had more obstructive disease (35.7% vs 23.3%, P < .001), lower lung allocation score (36.5 vs 41.1, P < .001), and longer waitlist time (P = .002). HCV D+/R- LT had similar risk of acute rejection (adjusted odds ratio [aOR], 0.87; P = .58), extracorporeal membranous oxygenation (aOR, 1.94; P = .10), and tracheostomy (aOR, 0.42; P = .16); similar median hospital stay (P = .07); and lower risk of ventilator > 48 hours (aOR, 0.68; P = .006). Adjusting for donor, recipient, and transplant characteristics, risk of all-cause graft failure and mortality were similar at 30 days, 1 year, and 3 years for HCV D+/R- versus HCV D-/R- LT (all P > .1), as well as for high- (≥20/year) versus low-volume LT centers and high- (≥5/year) versus low-volume HCV D+/R- LT centers (all P > .5).

CONCLUSIONS

HCV D+/R- and HCV D-/R- LT have similar outcomes at 3 years posttransplant. These results underscore the safety of HCV D+/R- LT and the potential benefit of expanding this practice further.

Association between Abdominal CT Measurements of Body Composition before Deceased Donor Liver Transplant with Posttransplant Outcomes

Background Pre-liver transplant (LT) sarcopenia is associated with poor survival. Methods exist for measuring body composition with use of CT scans; however, it is unclear which components best predict post-LT outcomes. Purpose To quantify the association between abdominal CT-based body composition measurements and post-LT mortality in a large North American cohort. Materials and Methods This was a retrospective cohort of adult first-time deceased-donor LT recipients from 2009 to 2018 who underwent pre-LT abdominal CT scans, including at the L3 vertebral level, at Johns Hopkins Hospital. Measurements included sarcopenia (skeletal muscle index [SMI] <50 in men and <39 in women), sarcopenic obesity, myosteatosis (skeletal muscle CT attenuation <41 mean HU for body mass index [BMI] <25 and <33 mean HU for BMI ≥25), visceral adipose tissue (VAT), subcutaneous adipose tissue (SAT), and VAT/SAT ratio. Covariates in the adjusted models were selected with use of least absolute shrinkage and selection operator regression with lambda chosen by means of 10-fold cross-validation. Cox proportional hazards models were used to quantify associations with post-LT mortality. Model discrimination was quantified using the Harrell C-statistic. Results A total of 454 recipients (median age, 57 years [IQR, 50-62 years]; 294 men) were evaluated. In the adjusted model, pre-LT sarcopenia was associated with a higher hazard ratio (HR) of post-LT mortality (HR, 1.6 [95% CI: 1.1, 2.4]; C-statistic, 0.64; P = .02). SMI was significantly negatively associated with survival after adjustment for covariates. There was no evidence that myosteatosis was associated with mortality (HR, 1.3 [95% CI: 0.86, 2.1]; C-statistic, 0.64; P = .21). There was no evidence that BMI (HR, 1.2 [95% CI: 0.95, 1.4]), VAT (HR, 1.0 [95% CI: 0.98, 1.1]), SAT (HR, 1.0 [95% CI: 0.97, 1.0]), and VAT/SAT ratio (HR, 1.1 [95% CI: 0.90, 1.4]) were associated with mortality (P = .15-.77). Conclusions Sarcopenia, as assessed on routine pre-liver transplant (LT) abdominal CT scans, was the only factor significantly associated with post-LT mortality. © RSNA, 2022 See also the editorial by Ruehm in this issue.

Racial disparities in post-transplant stroke and mortality following stroke in adult cardiac transplant recipients in the United States

Black heart transplant recipients have a higher mortality rate than white recipients 6-12 months after transplant. Whether there are racial disparities in post-transplant stroke incidence and all-cause mortality following post-transplant stroke among cardiac transplant recipients is unknown. Using a nationwide transplant registry, we assessed the association between race and incident post-transplant stroke using logistic regression and the association between race and mortality among adults who survived a post-transplant stroke using Cox proportional hazards regression. We found no evidence of an association between race and the odds of post-transplant stroke (OR = 1.00, 95% CI: 0.83-1.20). The median survival time of those with a post-transplant stroke in this cohort was 4.1 years (95% CI: 3.0, 5.4). There were 726 deaths among the 1139 patients with post-transplant stroke, including 127 deaths among 203 Black patients and 599 deaths among 936 white patients. Among post-transplant stroke survivors, Black transplant recipients experienced a 23% higher rate of mortality compared to white recipients (HR = 1.23, 95% CI: 1.00-1.52). This disparity is strongest in the period beyond the first 6 months and appears to be mediated by differences in the post-transplant setting of care between Black and white patients. The racial disparity in mortality outcomes was not evident in the past decade. The improved survival of Black patients in the recent decade may reflect overall protocol improvements for heart transplant recipients irrespective of race, such as advancements in surgical techniques and immediate postoperative care as well as increased awareness about reducing racial disparities.

Incidence of Statin-Associated Adverse Events in Kidney Transplant Recipients

BACKGROUND

Statins are the third most prescribed drug class in kidney transplant recipients as cardiovascular diseases is the leading cause of death in this population. However, statins' safety profile remains unclear in kidney transplant recipients who are uniquely burdened by concomitant immunosuppression and comorbidities. We conducted a national study to characterize the association of statin use with adverse events in kidney transplant recipients.

METHODS

We studied adult (≥18) single-organ kidney transplant recipients in 2006-2016 with Medicare as primary payer (n=57,699). We used prescription drug claims to capture statin use, and ICD-9/10 diagnosis codes to capture statin-related adverse events (post-transplant diabetes mellitus, hemorrhagic stroke, cataract, liver injury, and rhabdomyolysis). We conducted multivariable Cox regression for each outcome with statin use as a time-varying exposure.

RESULTS

Post-transplant diabetes mellitus was the most common outcome (5-year Kaplan-Meier incidence; 43% in statin users vs. 35% in non-users), followed by cataract (22% vs. 12%), liver injury (2% vs. 3%), hemorrhagic stroke (1.9% vs. 1.4%), and rhabdomyolysis (1.5% vs. 0.9%). In our multivariable analysis, statin use was associated with higher hazard of post-transplant diabetes mellitus (aHR=1.12 [95% CI, 1.07-1.18]), cataract (aHR=1.22 [1.14-1.31]), and rhabdomyolysis (aHR=1.37 [1.10-1.71]), but lower hazard of liver injury (aHR=0.82 [0.71-0.95]). Statin use was not associated with hemorrhagic stroke (aHR=1.04 [0.86-1.26]).

CONCLUSIONS

Statins appear to be generally well-tolerated in kidney transplant recipients. However, statin use might be associated with slightly higher risk of post-transplant diabetes mellitus, cataract, and rhabdomyolysis.

Outcomes after liver transplantation using deceased after circulatory death donors: A comparison of outcomes in the UK and the US

BACKGROUND AND AIMS

Identifying international differences in utilization and outcomes of liver transplantation (LT) after donation after circulatory death (DCD) donation provides a unique opportunity for benchmarking and population-level insight.

METHODS

Adult (≥18 years) LT data between 2008 and 2018 from the UK and US were used to assess mortality and graft failure after DCD LT. We used time-dependent Cox-regression methods to estimate hazard ratios (HR) for risk-adjusted short-term (0-90 days) and longer-term (90 days-5 years) outcomes.

RESULTS

One-thousand five-hundred-and-sixty LT receipts from the UK and 3426 from the US were included. Over the study period, the use of DCD livers increased from 15.7% to 23.9% in the UK compared to 5.1% to 7.6% in the US. In the UK, DCD donors were older (UK:51 vs. US:33 years) with longer cold ischaemia time (UK: 437 vs. US: 333 min). Recipients in the US had higher Model for End-stage Liver Disease (MELD) scores, higher body mass index, higher proportions of ascites, encephalopathy, diabetes and previous abdominal surgeries. No difference in the risk-adjusted short-term mortality or graft failure was observed between the countries. In the longer-term (90 days-5 years), the UK had lower mortality and graft failure (adj.mortality HR:UK: 0.63 (95% CI: 0.49-0.80); graft failure HR: UK: 0.72, 95% CI: 0.58-0.91). The cumulative incidence of retransplantation was higher in the UK (5 years: UK: 11.9% vs. 4.6%; p < .001).

CONCLUSIONS

For those receiving a DCD LT, longer-term post-transplant outcomes in the UK are superior to the US, however, significant differences in recipient illness, graft quality and access to retransplantation were seen between the two countries.

Does anybody really know what (the kidney median waiting) time is?

The median waiting time (MWT) to deceased donor kidney transplant is of interest to patients, clinicians, and the media but remains elusive due to both methodological and philosophical challenges. We used Organ Procurement and Transplantation Network data from January 2003 to March 2022 to estimate MWTs using various methods and timescales, applied overall, by era, and by candidate demographics. After rising for a decade, the overall MWT fell to 5.19 years between 2015 and 2018 and declined again to 4.05 years (April 2021 to March 2022), based on the Kaplan-Meier method applied to period-prevalent cohorts. MWTs differed markedly by blood type, donor service area, and pediatric vs adult status, but to a lesser degree by race/ethnicity. Choice of methodology affected the magnitude of these differences. Instead of waiting years for an answer, reliable kidney MWT estimates can be obtained shortly after a policy is implemented using the period-prevalent Kaplan-Meier approach, a theoretical but useful construct for which we found no evidence of bias compared with using incident cohorts. We recommend this method be used complementary to the competing risks approach, under which MWT is often inestimable, to fill the present information void concerning the seemingly simple question of how long it takes to get a kidney transplant in the United States.

Keratoplasty Registries: Lessons Learned

ABSTRACT

Clinical registries have been developed for decades in the field of ophthalmology, and they are especially well-suited to the study of keratoplasty practices. A comprehensive donor/recipient registry system can provide insight into donor, recipient, and surgical factors associated with immediate and long-term outcomes and adverse reactions. Furthermore, linkage with demographic databases can elucidate relationships with social determinants of health and potentially shape public policy. The vast sample size and multicenter nature of registries enable researchers to conduct sophisticated multivariate or multilayered analyses. In this review, we aim to emphasize the importance of registry data for keratoplasty practice and 1) summarize the structure of current keratoplasty registries; 2) examine the features and scientific contributions of the registries from Australia, the United Kingdom, Singapore, the Netherlands, Sweden, Eye Bank Association of America, and European Cornea and Cell Transplant registries; 3) compare registry-based studies with large single-site clinical studies; 4) compare registry-based studies with randomized control studies; and 5) make recommendations for future development of keratoplasty registries. Keratoplasty registries have increased our knowledge of corneal transplant practices and their outcomes. Future keratoplasty registry-based studies may be further strengthened by record linkage, data sharing, and international collaboration.

Organ Donation and Transplants During Major US Motorcycle Rallies

Importance

Large-scale motorcycle rallies attract thousands of attendees and are associated with increased trauma-related morbidity and mortality.

Objective

To examine the association of major US motorcycle rallies with the incidence of organ donation and transplants.

Design, Setting, and Participants

This population-based, retrospective cross-sectional study used data from the Scientific Registry of Transplant Recipients for deceased organ donors aged 16 years or older involved in a motor vehicle crash and recipients of organs from these donors from March 2005 to September 2021.

Exposure

Dates of 7 large US motorcycle rallies and regions near these events.

Main Outcomes and Measures

The main outcomes were incidence of motor vehicle crash-related organ donation and number of patients receiving a solid organ transplant from these donors. An event study design was used to estimate adjusted rates of organ donation during the dates of 7 major US motorcycle rallies compared with the 4 weeks before and after the rallies in rally-affected and rally-unaffected (control) regions. Donor and recipient characteristics and metrics of organ quality were compared between rally and nonrally dates.

Results

The study included 10 798 organ donors (70.9% male; mean [SD] age, 32.5 [13.7] years) and 35 329 recipients of these organs (64.0% male; 49.3 [15.5] years). During the rally dates, there were 406 organ donors and 1400 transplant recipients. During the 4 weeks before and after the rallies, there were 2332 organ donors and 7714 transplant recipients. Donors and recipients during rally and nonrally dates were similar in demographic and clinical characteristics, measures of organ quality, measures of recipient disease severity, and recipient waiting time. During rallies, there were 21% more organ donors per day (incidence rate ratio [IRR], 1.21; 95% CI, 1.09-1.35; P = .001) and 26% more transplant recipients per day (IRR, 1.26; 95% CI, 1.12-1.42; P < .001) compared with the 4 weeks before and after the rallies in the regions where they were held.

Conclusions and Relevance

In this cross-sectional study, major motorcycle rallies in the US were associated with increased incidence of organ donation and transplants. While safety measures to minimize morbidity and mortality during motorcycle rallies should be prioritized, this study showed the downstream association of these events with organ donation and transplants.

Hyperparathyroidism at 1 year after kidney transplantation is associated with graft loss

BACKGROUND

Hyperparathyroidism persists in many patients after kidney transplantation. The purpose of this study was to evaluate the association between post-transplant hyperparathyroidism and kidney transplantation outcomes.

METHODS

We identified 824 participants from a prospective longitudinal cohort of adult patients who underwent kidney transplantation at a single institution between December 2008 and February 2020. Parathyroid hormone levels before and after kidney transplantation were abstracted from medical records. Post-transplant hyperparathyroidism was defined as parathyroid hormone level ≥70 pg/mL 1 year after kidney transplantation. Cox proportional hazards models were used to estimate the adjusted hazard ratios of mortality and death-censored graft loss by post-transplant hyperparathyroidism. Models were adjusted for age, sex, race/ethnicity, college education, parathyroid hormone level before kidney transplantation, cause of kidney failure, and years on dialysis before kidney transplantation. A Wald test for interactions was used to evaluate the risk of death-censored graft loss by age, sex, and race.

RESULTS

Of 824 recipients, 60.9% had post-transplant hyperparathyroidism. Compared with non-hyperparathyroidism patients, those with post-transplant hyperparathyroidism were more likely to be Black (47.2% vs 32.6%), undergo dialysis before kidney transplantation (86.9% vs 76.6%), and have a parathyroid hormone level ≥300 pg/mL before kidney transplantation (26.8% vs 9.5%) (all P < .001). Patients with post-transplant hyperparathyroidism had a 1.6-fold higher risk of death-censored graft loss (adjusted hazard ratio = 1.60, 95% confidence interval: 1.02-2.49) compared with those without post-transplant hyperparathyroidism. This risk more than doubled in those with parathyroid hormone ≥300 pg/mL 1 year after kidney transplantation (adjusted hazard ratio = 4.19, 95% confidence interval: 1.95-9.03). The risk of death-censored graft loss did not differ by age, sex, or race (all Pinteraction > .05). There was no association between post-transplant hyperparathyroidism and mortality.

CONCLUSION

The risk of graft loss was significantly higher among patients with post-transplant hyperparathyroidism when compared with patients without post-transplant hyperparathyroidism.

Machine learning-based techniques to improve lung transplantation outcomes and complications: a systematic review

BACKGROUND

Machine learning has been used to develop predictive models to support clinicians in making better and more reliable decisions. The high volume of collected data in the lung transplant process makes it possible to extract hidden patterns by applying machine learning methods. Our study aims to investigate the application of machine learning methods in lung transplantation.

METHOD

A systematic search was conducted in five electronic databases from January 2000 to June 2022. Then, the title, abstracts, and full text of extracted articles were screened based on the PRISMA checklist. Then, eligible articles were selected according to inclusion criteria. The information regarding developed models was extracted from reviewed articles using a data extraction sheet.

RESULTS

Searches yielded 414 citations. Of them, 136 studies were excluded after the title and abstract screening. Finally, 16 articles were determined as eligible studies that met our inclusion criteria. The objectives of eligible articles are classified into eight main categories. The applied machine learning methods include the Support vector machine (SVM) (n = 5, 31.25%) technique, logistic regression (n = 4, 25%), Random Forests (RF) (n = 4, 25%), Bayesian network (BN) (n = 3, 18.75%), linear regression (LR) (n = 3, 18.75%), Decision Tree (DT) (n = 3, 18.75%), neural networks (n = 3, 18.75%), Markov Model (n = 1, 6.25%), KNN (n = 1, 6.25%), K-means (n = 1, 6.25%), Gradient Boosting trees (XGBoost) (n = 1, 6.25%), and Convolutional Neural Network (CNN) (n = 1, 6.25%). Most studies (n = 11) employed more than one machine learning technique or combination of different techniques to make their models. The data obtained from pulmonary function tests were the most used as input variables in predictive model development. Most studies (n = 10) used only post-transplant patient information to develop their models. Also, UNOS was recognized as the most desirable data source in the reviewed articles. In most cases, clinicians succeeded to predict acute diseases incidence after lung transplantation (n = 4) or estimate survival rate (n = 4) by developing machine learning models.

CONCLUSION

The outcomes of these developed prediction models could aid clinicians to make better and more reliable decisions by extracting new knowledge from the huge volume of lung transplantation data.

Transplantation Amid a Pandemic: The Fall and Rise of Kidney Transplantation in the United States

Following the outbreak of coronavirus disease 2019 (COVID-19) in the United States, the number of kidney waitlist additions and living-donor and deceased-donor kidney transplants (LDKT/DDKT) decreased substantially but began recovering within a few months. Since then, there have been several additional waves of infection, most notably, the Delta and Omicron surges beginning in August and December 2021, respectively.

Methods

Using SRTR data, we compared observed waitlist registrations, waitlist mortality, waitlist removal due to deteriorating condition, LDKT, and DDKT over 5 distinct pandemic periods to expected events based on calculations from preepidemic data while accounting for seasonality and secular trends.

Results

Although the number of daily waitlist additions has been increasing since May 2020, the size of the active waitlist has consistently declined, reaching a minimum of 52 556 on February 27, 2022. The recent Omicron surge knocked LDKT from 25% below baseline (incidence rate ratio [IRR] = _0.690.75_0.81) during the Delta wave to 38% below baseline (IRR = _0.580.62_0.67). DDKT, however, was less affected by the Omicron wave (IRR = _0.850.89_0.93 and _0.880.92_0.96 during the Delta and Omicron waves, respectively). Waitlist death decreased from 56% above baseline (IRR = _1.431.56_1.70) during Delta to 41% above baseline during Omicron, whereas waitlist removal due to deteriorating condition remained at baseline/expected levels during the Delta wave (IRR = _0.931.02_1.12) and the Omicron wave (IRR = _0.991.07_1.16).

Conclusions

Despite exceptionally high COVID-19 incidence during the Omicron wave, the transplant system responded similarly to prior waves that imposed a lesser disease burden, demonstrating the transplant system's growing adaptations and resilience to this now endemic disease.

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.

Trends and three-year outcomes of hepatitis C virus-viremic donor heart transplant for hepatitis C virus-seronegative recipients

Objective

Heart transplants (HTs) from hepatitis C virus (HCV)-viremic donors to HCV-seronegative recipients (HCV D+/R-) have good 6-month outcomes, but practice uptake and long-term outcomes overall and among candidates on mechanical circulatory support (MCS) have yet to be established.

Methods

Using the Scientific Registry of Transplant Recipients, we identified US adult HCV-seronegative HT recipients (R-) from 2015 to 2021. We classified donors as HCV-seronegative (D-) or HCV-viremic (D+). We used multivariable regression to compare post-HT extracorporeal membranous oxygenation, dialysis, pacemaker, acute rejection, and risk of post-HT mortality between HCV D+/R- and HCV D-/R-. Models were adjusted for donor, recipient, and transplant characteristics and center HT volume. We performed subgroup analyses of recipients bridged with MCS.

Results

From 2015 to 2021, the number of HCV D+/R- HT increased from 1 to 181 and the number of centers performing HCV D+/R- HT increased from 1 to 60. Compared with HCV D-/R- recipients, HCV D+/R- versus D-/R- recipients overall and among patients bridged with MCS had similar odds of post-HT extracorporeal membranous oxygenation, dialysis, pacemaker, and acute rejection; and mortality risk at 30 days, 1 year, and 3 years (all P > .05). High center HT volume but not HCV D+/R- volume (<5 vs >5 in any year) was associated with lower mortality for HCV D+/R- HT.

Conclusions

HCV D+/R- and D-/R- HT have similar outcomes at 3 years' posttransplant. These results underscore the opportunity provided by HCV D+/R- HT, including among the growing population bridged with MCS, and the potential benefit of further expanding use of HCV+ allografts.