The current landscape of in situ and ex-situ machine perfusion utilization for liver grafts from cardiac donation after circulatory death donors in the US.

Donation after circulatory death (DCD) is driving the increase in deceased organ donors in the United States. Normothermic regional perfusion (NRP) and ex-situ machine perfusion (es-MP) have been instrumental in improving liver transplant outcomes and graft utilization. This study examines the current landscape of liver utilization from cardiac DCD donors in the US. Using the UNOS STAR file, all adult (≥ 18 years old) DCD donors in the US in which the heart was used for transplantation from October 1, 2020, to September 30, 2023, were compared using procurement technique (NRP versus super rapid recovery [SRR]) and storage strategy (es-MP versus static cold storage [SCS]). 188 livers were transplanted from 309 TA-NRP donors (61% utilization) versus 305 (56%) liver transplants from 544 SRR donors. Es-MP was used in 20% (n= 38) of NRP cases versus 32% (98) of SRR cases. 281 (59%) of liver grafts were exposed to NRP, es-MP, or both. While there is widespread utilization of machine perfusion, more research is needed to determine optimal graft management strategies, particularly concerning the use of multiple technologies in complementary ways. More complete data collection is necessary at a national level to address these important research questions.

A Common Longitudinal Intensive Care Unit data Format (CLIF) to enable multi-institutional federated critical illness research.

Background: Critical illness, or acute organ failure requiring life support, threatens over five million American lives annually. Electronic health record (EHR) data are a source of granular information that could generate crucial insights into the nature and optimal treatment of critical illness. However, data management, security, and standardization are barriers to large-scale critical illness EHR studies. Methods: A consortium of critical care physicians and data scientists from eight US healthcare systems developed the Common Longitudinal Intensive Care Unit (ICU) data Format (CLIF), an open-source database format that harmonizes a minimum set of ICU Data Elements for use in critical illness research. We created a pipeline to process adult ICU EHR data at each site. After development and iteration, we conducted two proof-of-concept studies with a federated research architecture: 1) an external validation of an in-hospital mortality prediction model for critically ill patients and 2) an assessment of 72-hour temperature trajectories and their association with mechanical ventilation and in-hospital mortality using group-based trajectory models. Results: We converted longitudinal data from 94,356 critically ill patients treated in 2020-2021 (mean age 60.6 years [standard deviation 17.2], 30% Black, 7% Hispanic, 45% female) across 8 health systems and 33 hospitals into the CLIF format, The in-hospital mortality prediction model performed well in the health system where it was derived (0.81 AUC, 0.06 Brier score). Performance across CLIF consortium sites varied (AUCs: 0.74-0.83, Brier scores: 0.06-0.01), and demonstrated some degradation in predictive capability. Temperature trajectories were similar across health systems. Hypothermic and hyperthermic-slow-resolver patients consistently had the highest mortality. Conclusions: CLIF facilitates efficient, rigorous, and reproducible critical care research. Our federated case studies showcase CLIF's potential for disease sub-phenotyping and clinical decision-support evaluation. Future applications include pragmatic EHR-based trials, target trial emulations, foundational multi-modal AI models of critical illness, and real-time critical care quality dashboards.

Graft Survival of En Bloc Deceased Donor Kidneys Transplants Compared With Single Kidney Transplants.

BACKGROUND: The US Kidney Allocation System allocates en bloc deceased donor kidney grafts from donors <18 kg in sequence A along with single kidney transplants (SKTs) from kidney donor profile index (KDPI) top 20% donors. Although en bloc grafts outperform SKT grafts holding donor weight constant, it is unclear if en bloc grafts from the smallest pediatric donors perform the same as top 20% KDPI SKTs. METHODS: Using the Scientific Registry of Transplant Recipients, we compared the donor characteristics and graft survival of en bloc grafts from the smallest donors (<8 kg) and from larger donors (≥8 kg) with SKTs by KDPI sequence for transplants performed in 2021. RESULTS: Larger donor en blocs had similar 1-y survival to sequence A SKTs estimated by the Kaplan-Meier method (96% versus 96%, P = 0.9), but the smallest donor en blocs had significantly shorter 1-y survival than those SKTs (80% versus 96%, P < 0.01). Using transplants from 2010 to 2012, the smallest donor en blocs had similar 10-y survival to sequence A SKTs (69% versus 64%, P = 0.3). CONCLUSIONS: These findings suggest that future updates of the Kidney Allocation System should include a score specific to pediatric donors to account for these differences in en bloc graft survival.

Association of Race and Ethnicity With High Longevity Deceased Donor Kidney Transplantation Under the US Kidney Allocation System.

RATIONALE & OBJECTIVE: The US Kidney Allocation System (KAS) prioritizes candidates with a≤20% estimated posttransplant survival (EPTS) to receive high-longevity kidneys defined by a≤20% Kidney Donor Profile Index (KDPI). Use of EPTS in the KAS deprioritizes candidates with older age, diabetes, and longer dialysis durations. We assessed whether this use also disadvantages race and ethnicity minority candidates, who are younger but more likely to have diabetes and longer durations of kidney failure requiring dialysis. STUDY DESIGN: Observational cohort study. SETTING & PARTICIPANTS: Adult candidates for and recipients of kidney transplantation represented in the Scientific Registry of Transplant Recipients from January 2015 through December 2020. EXPOSURE: Race and ethnicity. OUTCOME: Age-adjusted assignment to≤20% EPTS, transplantation of a≤20% KDPI kidney, and posttransplant survival in longevity-matched recipients by race and ethnicity. ANALYTIC APPROACH: Multivariable logistic regression, Fine-Gray competing risks survival analysis, and Kaplan-Meier and Cox proportional hazards methods. RESULTS: The cohort included 199,444 candidates (7% Asian, 29% Black, 19% Hispanic or Latino, and 43% White) listed for deceased donor kidney transplantation. Non-White candidates had significantly higher rates of diabetes, longer dialysis duration, and were younger than White candidates. Adjusted for age, Asian, Black, and Hispanic or Latino candidates had significantly lower odds of having a ETPS score of≤20% (odds ratio, 0.86 [95% CI, 0.81-0.91], 0.52 [95% CI, 0.50-0.54], and 0.49 [95% CI, 0.47-0.51]), and were less likely to receive a≤20% KDPI kidney (sub-hazard ratio, 0.70 [0.66-0.75], 0.89 [0.87-0.92], and 0.73 [0.71-0.76]) compared with White candidates. Among recipients with≤20% EPTS scores transplanted with a≤20% KDPI deceased donor kidney, Asian and Hispanic recipients had lower posttransplant mortality (HR, 0.45 [0.27-0.77] and 0.63 [0.47-0.86], respectively) and Black recipients had higher but not statistically significant posttransplant mortality (HR, 1.22 [0.99-1.52]) compared with White recipients. LIMITATIONS: Provider reported race and ethnicity data and 5-year post transplant follow-up period. CONCLUSIONS: The US kidney allocation system is less likely to identify race and ethnicity minority candidates as having a≤20% EPTS score, which triggers allocation of high-longevity deceased donor kidneys. These findings should inform the Organ Procurement and Transplant Network about how to remedy the race and ethnicity disparities introduced through KAS's current approach of allocating allografts with longer predicted longevity to recipients with longer estimated posttransplant survival. PLAIN-LANGUAGE SUMMARY: The US Kidney Allocation System prioritizes giving high-longevity, high-quality kidneys to patients on the waiting list who have a high estimated posttransplant survival (EPTS) score. EPTS is calculated based on the patient's age, whether the patient has diabetes, whether the patient has a history of organ transplantation, and the number of years spent on dialysis. Our analyses show that Asian, Black or African American, and Hispanic or Latino patients were less likely to receive high-longevity kidneys compared with White patients, despite having similar or better posttransplant survival outcomes.

Knowledge gaps in heart and lung donation after the circulatory determination of death: Report of a workshop of the National Heart, Lung, and Blood Institute.

In a workshop sponsored by the U.S. National Heart, Lung, and Blood Institute, experts identified current knowledge gaps and research opportunities in the scientific, conceptual, and ethical understanding of organ donation after the circulatory determination of death and its technologies. To minimize organ injury from warm ischemia and produce better recipient outcomes, innovative techniques to perfuse and oxygenate organs postmortem in situ, such as thoracoabdominal normothermic regional perfusion, are being implemented in several medical centers in the US and elsewhere. These technologies have improved organ outcomes but have raised ethical and legal questions. Re-establishing donor circulation postmortem can be viewed as invalidating the condition of permanent cessation of circulation on which the earlier death determination was made and clamping arch vessels to exclude brain circulation can be viewed as inducing brain death. Alternatively, TA-NRP can be viewed as localized in-situ organ perfusion, not whole-body resuscitation, that does not invalidate death determination. Further scientific, conceptual, and ethical studies, such as those identified in this workshop, can inform and help resolve controversies raised by this practice.

Development and Validation of a Risk Score Predicting Death Without Transplant in Adult Heart Transplant Candidates.

Importance: The US heart allocation system prioritizes medically urgent candidates with a high risk of dying without transplant. The current therapy-based 6-status system is susceptible to manipulation and has limited rank ordering ability. Objective: To develop and validate a candidate risk score that incorporates current clinical, laboratory, and hemodynamic data. Design, Setting, and Participants: A registry-based observational study of adult heart transplant candidates (aged ≥18 years) from the US heart allocation system listed between January 1, 2019, and December 31, 2022, split by center into training (70%) and test (30%) datasets. Adult candidates were listed between January 1, 2019, and December 31, 2022. Main Outcomes and Measures: A US candidate risk score (US-CRS) model was developed by adding a predefined set of predictors to the current French Candidate Risk Score (French-CRS) model. Sensitivity analyses were performed, which included intra-aortic balloon pumps (IABP) and percutaneous ventricular assist devices (VAD) in the definition of short-term mechanical circulatory support (MCS) for the US-CRS. Performance of the US-CRS model, French-CRS model, and 6-status model in the test dataset was evaluated by time-dependent area under the receiver operating characteristic curve (AUC) for death without transplant within 6 weeks and overall survival concordance (c-index) with integrated AUC. Results: A total of 16 905 adult heart transplant candidates were listed (mean [SD] age, 53 [13] years; 73% male; 58% White); 796 patients (4.7%) died without a transplant. The final US-CRS contained time-varying short-term MCS (ventricular assist-extracorporeal membrane oxygenation or temporary surgical VAD), the log of bilirubin, estimated glomerular filtration rate, the log of B-type natriuretic peptide, albumin, sodium, and durable left ventricular assist device. In the test dataset, the AUC for death within 6 weeks of listing for the US-CRS model was 0.79 (95% CI, 0.75-0.83), for the French-CRS model was 0.72 (95% CI, 0.67-0.76), and 6-status model was 0.68 (95% CI, 0.62-0.73). Overall c-index for the US-CRS model was 0.76 (95% CI, 0.73-0.80), for the French-CRS model was 0.69 (95% CI, 0.65-0.73), and 6-status model was 0.67 (95% CI, 0.63-0.71). Classifying IABP and percutaneous VAD as short-term MCS reduced the effect size by 54%. Conclusions and Relevance: In this registry-based study of US heart transplant candidates, a continuous multivariable allocation score outperformed the 6-status system in rank ordering heart transplant candidates by medical urgency and may be useful for the medical urgency component of heart allocation.

Post-transplant survival after normothermic regional perfusion versus direct procurement and perfusion in donation after circulatory determination of death in heart transplantation.

BACKGROUND: Since 2019, the annual transplantation rate of hearts donated following circulatory death (DCD) has increased significantly in the United States. The 2 major heart procurement techniques following circulatory death are direct procurement and perfusion (DPP) and normothermic regional perfusion (NRP). Post-transplant survival for heart recipients has not been compared between these 2 techniques. METHODS: This observational study uses data on adult heart transplants from donors after circulatory death from January 1, 2019 to December 31, 2021 in the Scientific Registry of Transplant Recipients. We identified comparable transplant cases across procurement types using propensity-score matching and measured the association between procurement technique and 1-year post-transplant survival using Kaplan-Meier and Cox proportional hazards model stratefied by matching pairs. RESULTS: Among 318 DCD heart transplants, 216 (68%) were procured via DPP, and 102 (32%) via NRP. Among 22 transplant centers that accepted circulatory-death donors, 3 used NRP exclusively, and 5 used both procurement techniques. After propensity-score matching on recipient and donor factors, there was no significant difference in 1-year post-transplant survival (93.1% for NRP vs 91.1% for DPP, p = 0.79) between procurement techniques. CONCLUSIONS: NRP and DPP procurements are associated with similar 1-year post-transplant survival. If NRP is ethically permissible and improves outcomes for abdominal organs, it should be the preferred procurement technique for DCD hearts.

Hospital Policy Variation in Addressing Decisions to Withhold and Withdraw Life-Sustaining Treatment.

BACKGROUND: Sociodemographic disparities in physician decisions to withhold and withdraw life-sustaining treatment exist. Little is known about the content of hospital policies that guide physicians involved in these decisions. RESEARCH QUESTION: What is the prevalence of US hospitals with policies that address withholding and withdrawing life-sustaining treatment; how do these policies approach ethically controversial scenarios; and how do these policies address sociodemographic disparities in decisions to withhold and withdraw life-sustaining treatment? STUDY DESIGN AND METHODS: This national cross-sectional survey assessed the content of hospital policies addressing decisions to withhold or withdraw life-sustaining treatment. We distributed the survey electronically to American Society for Bioethics and Humanities members between July and August 2023 and descriptively analyzed responses. RESULTS: Among 93 respondents from hospitals or hospital systems representing all 50 US states, Puerto Rico, and Washington, DC, 92% had policies addressing decisions to withhold or withdraw life-sustaining treatment. Hospitals varied in their stated guidance, permitting life-sustaining treatment to be withheld or withdrawn in cases of patient or surrogate request (82%), physiologic futility (81%), and potentially inappropriate treatment (64%). Of the 8% of hospitals with policies that addressed patient sociodemographic disparities in decisions to withhold or withdraw life-sustaining treatment, these policies provided opposing recommendations to either exclude sociodemographic factors in decision-making or actively acknowledge and incorporate these factors in decision-making. Only 3% of hospitals had policies that recommended collecting and maintaining information about patients for whom life-sustaining treatment was withheld or withdrawn that could be used to identify disparities in decision-making. INTERPRETATION: Although most surveyed US hospital policies addressed withholding or withdrawing life-sustaining treatment, these policies varied widely in criteria and processes. Surveyed policies also rarely addressed sociodemographic disparities in these decisions.

Risk Factors for Hospital Readmission in Patients With Interstitial Lung Disease.

BACKGROUND: Little is known about the rates, causes, or risk factors for hospital readmission among patients with interstitial lung disease (ILD). We investigated the prevalence, features, and comorbidities of subjects hospitalized with ILD and their subsequent re-hospitalizations in this retrospective study. METHODS: A retrospective analysis of subjects enrolled in the University of Chicago ILD Natural History registry was conducted. Demographic data, comorbidities, and timing and cause of subsequent hospitalizations were collected from the medical record. The primary outcome was time to first readmission via a cause-specific Cox hazards model with a sensitivity analysis with the Fine-Gray cumulative hazard model; the secondary outcome was the number of hospitalizations per subject via a Poisson multivariable model. RESULTS: Among 1,796 patients with ILD, 443 subjects were hospitalized, with 978 total hospitalizations; 535 readmissions were studied, 282 (53%) for a respiratory indication. For the outcome of time to readmission, Black race was the only subject characteristic associated with an increased hazard of readmission in the Cox model (hazard ratio 1.50, P = .03) while Black race, hypersensitivity pneumonitis, and sarcoidosis were associated with increased hazard of readmission in the Fine-Gray model. Black race, female sex, atrial fibrillation, obstructive lung disease, and pulmonary hypertension were associated with an increased number of hospitalizations in the Poisson model. CONCLUSIONS: We demonstrated that hospital readmission from any cause was a common occurrence in subjects with ILD. Further efforts to improve quality of life among these subjects could focus on risk scores for readmission, mitigating racial health disparities, and treatment of comorbidities.

Do-Not-Resuscitate Orders by COVID-19 Status Throughout the First Year of the COVID-19 Pandemic.

BACKGROUND: At the beginning of the COVID-19 pandemic, whether performing CPR on patients with COVID-19 would be effective or increase COVID-19 transmission to health care workers was unclear. RESEARCH QUESTION: Did the prevalence of do-not-resuscitate (DNR) orders by COVID-19 status change over the first year of the pandemic as risks such as COVID-19 transmission to health care workers improved? STUDY DESIGN AND METHODS: This cross-sectional study assessed DNR orders for all adult patients admitted to ICUs at two academic medical centers in Chicago, IL, between April 2020 and April 2021. DNR orders by COVID-19 status were assessed using risk-adjusted mixed-effects logistic regression and propensity score matching by patient severity of illness. RESULTS: The study population of 3,070 critically ill patients were 46% Black, 53% male, with median age (interquartile range [IQR]) 63 (50-73) years. Eighteen percent were COVID-19 positive and 27% had a DNR order. Black and Latinx patients had higher absolute rates of DNR orders than White patients (30% vs 29% vs 23%; P = .006). After adjustment for patient characteristics, illness severity, and hospital location, DNR orders were more likely in patients with COVID-19 in the nonpropensity score-matched (n = 3,070; aOR, 2.01; 95% CI, 1.64-2.38) and propensity score-matched (n = 1,118; aOR, 1.91; 95% CI, 1.45-2.52) cohorts. The prevalence of DNR orders remained higher for patients with COVID-19 than patients without COVID-19 during all months of the study period (difference in prevalence over time, P = .751). INTERPRETATION: In this multihospital study, DNR orders remained persistently higher for patients with COVID-19 vs patients without COVID-19 with similar severity of illness during the first year of the pandemic. The specific reasons why DNR orders remained persistently elevated for patients with COVID-19 should be assessed in future studies, because these changes may continue to affect COVID-19 patient care and outcomes.

Association of preadmission insomnia symptoms with objective in-hospital sleep and clinical outcomes among hospitalized patients.

STUDY OBJECTIVES: To determine the prevalence of preadmission insomnia symptoms among hospitalized patients and assess the association of insomnia symptoms with objective in-hospital sleep and clinical outcomes. METHODS: We conducted a prospective cohort study of medicine inpatients (age ≥ 50, no previously diagnosed sleep disorders). Participants answered the Insomnia Severity Index (ISI) questionnaire to assess for preadmission insomnia symptoms (scored 0-28; higher scores suggest more insomnia symptoms). Sleep duration and efficiency were measured with actigraphy. Participants self-reported 30-day postdischarge readmissions and emergency department and/or urgent care visits. RESULTS: Of 568 participants, 49% had ISI scores suggestive of possible undiagnosed insomnia (ISI ≥ 8). Higher ISI scores were associated with shorter sleep duration [ß = -2.6, 95% confidence interval (CI) -4.1 to -1.1, P = .001] and lower sleep efficiency (ß = -0.39, 95% CI -0.63 to -0.15, P = .001). When adjusted for age, sex, body mass index, and comorbidities, higher ISI scores were associated with longer length of stay (incidence rate ratio 1.01, 95% CI 1.00-1.02, P = .011), increased risk of 30-day readmission (odds ratio 1.04, 95% CI 1.01-1.07, P = .018), and increased risk of 30-day emergency department or urgent care visit (odds ratio 1.04, 95% CI 1.00-1.07, P = .043). CONCLUSIONS: Among medicine inpatients, there was a high prevalence of preadmission insomnia symptoms suggestive of possible undiagnosed insomnia. Participants with higher ISI scores slept less with lower sleep efficiency during hospitalization. Higher ISI scores were associated with longer length of stay, increased risk of a 30-day postdischarge readmission, and increased risk of a 30-day postdischarge emergency department or urgent care visit. CITATION: Neborak JM, Press VG, Parker WF, et al. Association of preadmission insomnia symptoms with objective in-hospital sleep and clinical outcomes among hospitalized patients. J Clin Sleep Med. 2024;20(5):681-687.

Pharmacotherapy and pulmonary fibrosis risk after SARS-CoV-2 infection: a prospective nationwide cohort study in the United States.

Background: Pulmonary fibrosis is characterized by lung parenchymal destruction and can increase morbidity and mortality. Pulmonary fibrosis commonly occurs following hospitalization for SARS-CoV-2 infection. As there are medications that modify pulmonary fibrosis risk, we investigated whether distinct pharmacotherapies (amiodarone, cancer chemotherapy, corticosteroids, and rituximab) are associated with differences in post-COVID-19 pulmonary fibrosis incidence. Methods: We used the National COVID-19 Cohort Collaboration (N3C) Data Enclave, which aggregates and harmonizes COVID-19 data across the United States, to assess pulmonary fibrosis incidence documented at least 60 days after COVID-19 diagnosis among adults hospitalized between January 1st, 2020 and July 6th, 2022 without pre-existing pulmonary fibrosis. We used propensity scores to match pre-COVID-19 drug-exposed and unexposed cohorts (1:1) based on covariates with known influence on pulmonary fibrosis incidence, and estimated the association of drug exposure with risk for post-COVID-19 pulmonary fibrosis. Sensitivity analyses considered pulmonary fibrosis incidence documented at least 30- or 90-days post-hospitalization and pulmonary fibrosis incidence in the COVID-19-negative N3C population. Findings: Among 5,923,394 patients with COVID-19, we analyzed 452,951 hospitalized adults, among whom pulmonary fibrosis incidence was 1.1 per 100-person-years. 277,984 hospitalized adults with COVID-19 were included in our primary analysis, among whom all drug exposed cohorts were well-matched to unexposed cohorts (standardized mean differences <0.1). The post-COVID-19 pulmonary fibrosis incidence rate ratio (IRR) was 2.5 (95% CI 1.2-5.1, P = 0.01) for rituximab, 1.6 (95% CI 1.3-2.0, P < 0.0001) for chemotherapy, and 1.2 (95% CI 1.0-1.3, P = 0.02) for corticosteroids. Amiodarone exposure had no significant association with post-COVID-19 pulmonary fibrosis (IRR = 0.8, 95% CI 0.6-1.1, P = 0.24). In sensitivity analyses, pre-COVID-19 corticosteroid use was not consistently associated with post-COVID-19 pulmonary fibrosis. In the COVID-19 negative hospitalized population (n = 1,240,461), pulmonary fibrosis incidence was lower overall (0.6 per 100-person-years) and for patients exposed to all four drugs. Interpretation: Recent rituximab or cancer chemotherapy before COVID-19 infection in hospitalized patients is associated with increased risk for post-COVID-19 pulmonary fibrosis. Funding: The analyses described in this publication were conducted with data or tools accessed through the NCATS N3C Data Enclave https://covid.cd2h.org and N3C Attribution & Publication Policy v1.2-2020-08-25b supported by NIHK23HL146942, NIHK08HL150291, NIHK23HL148387, NIHUL1TR002389, NCATSU24 TR002306, and a SECURED grant from the Walder Foundation/Center for Healthcare Delivery Science and Innovation, University of Chicago. WFP received a grant from the Greenwall Foundation. This research was possible because of the patients whose information is included within the data and the organizations (https://ncats.nih.gov/n3c/resources/data-contribution/data-transfer-agreement-signatories) and scientists who have contributed to the on-going development of this community resource (https://doi.org/10.1093/jamia/ocaa196).

Fair Allocation of Scarce CAR T-Cell Therapies for Relapsed/Refractory Multiple Myeloma.

This Viewpoint discusses the unfairness of current CAR T-cell therapy allocation practices and offers alternative methods to more fairly allocate therapy.

The Accuracy of Nonstandardized MELD/PELD Score Exceptions in the Pediatric Liver Allocation System.

BACKGROUND: In the United States, over half of pediatric candidates receive exceptions and status upgrades that increase their allocation model of end-stage liver disease/pediatric end-stage liver disease (MELD/PELD) score above their laboratory MELD/PELD score. We determined whether these "nonstandardized" MELD/PELD exceptions accurately depict true pretransplant mortality risk. METHODS: Using data from the Scientific Registry of Transplant Recipients, we identified pediatric candidates (<18 y of age) with chronic liver failure added to the waitlist between June 2016 and September 2021 and estimated all-cause pretransplant mortality with mixed-effects Cox proportional hazards models that treated allocation MELD/PELD and exception status as time-dependent covariates. We also estimated concordance statistics comparing the performance of laboratory MELD/PELD with allocation MELD/PELD. We then compared the proportion of candidates with exceptions before and after the establishment of the National Liver Review Board. RESULTS: Out of 2026 pediatric candidates listed during our study period, 403 (19.9%) received an exception within a week of listing and 1182 (58.3%) received an exception before delisting. Candidates prioritized by their laboratory MELD/PELD scores had an almost 9 times greater risk of pretransplant mortality compared with candidates who received the same allocation score from an exception (hazard ratio 8.69; 95% confidence interval, 4.71-16.03; P < 0.001). The laboratory MELD/PELD score without exceptions was more accurate than the allocation MELD/PELD score with exceptions (Harrell's c-index 0.843 versus 0.763). The proportion of patients with an active exception at the time of transplant decreased significantly after the National Liver Review Board was implemented (67.4% versus 43.4%, P < 0.001). CONCLUSIONS: Nonstandardized exceptions undermine the rank ordering of pediatric candidates with chronic liver failure.

Association of high-priority exceptions with waitlist mortality among heart transplant candidates.

BACKGROUND: The US heart allocation system ranks candidates using six categorical status levels. Transplant programs can request exceptions to increase a candidate's status level if they believe their candidate has the same medical urgency as candidates who meet the standard criteria for that level. We aimed to determine if exception candidates have the same medical urgency as standard candidates. METHODS: Using the Scientific Registry of Transplant Recipients, we constructed a longitudinal waitlist history dataset of adult heart-only transplant candidates listed between October 18, 2018 and December 1, 2021. We estimated the association between exceptions and waitlist mortality with a mixed-effects Cox proportional hazards model that treated status and exceptions as time-dependent covariates. RESULTS: Out of 12,458 candidates listed during the study period, 2273 (18.2%) received an exception at listing and 1957 (15.7%) received an exception after listing. After controlling for status, exception candidates had approximately half the risk of waitlist mortality as standard candidates (hazard ratio [HR] 0.55, 95% confidence interval [CI] [0.41, 0.73], p < .001). Exceptions were associated with a 51% lower risk of waitlist mortality among Status 1 candidates (HR 0.49, 95% CI [0.27, 0.91], p = .023) and a 61% lower risk among Status 2 candidates (HR 0.39, 95% CI [0.24, 0.62], p < .001). CONCLUSIONS: Under the new heart allocation policy, exception candidates had significantly lower waitlist mortality than standard candidates, including exceptions for the highest priority statuses. These results suggest that candidates with exceptions, on average, have a lower level of medical urgency than candidates who meet standard criteria.

The Accuracy of Initial U.S. Heart Transplant Candidate Rankings.

BACKGROUND: The U.S. heart allocation system ranks candidates with only 6 treatment-based categorical "statuses" and ignores many objective patient characteristics. OBJECTIVES: This study sought to determine the effectiveness of the standard 6-status ranking system and several novel prediction models in identifying the most urgent heart transplant candidates. METHODS: The primary outcome was death before receipt of a heart transplant. The accuracy of the 6-status system was evaluated using Harrell's C-index and log-rank tests of Kaplan-Meier estimated survival by status for candidates listed postpolicy (November 2018 to March 2020) in the Scientific Registry of Transplant Recipients data set. The authors then developed Cox proportional hazards models and random survival forest models using prepolicy data (2010-2017). The predictor variables included age, diagnosis, laboratory measurements, hemodynamics, and supportive treatment at the time of listing. The performance of these models was compared with the candidate's 6-status ranking in the postpolicy data. RESULTS: Since policy implementation, the 6-status ranking at listing has had moderate ability to rank-order candidates (C-index: 0.67). Statuses 4 and 6 had no significant difference in survival (P = 0.80), and status 5 had lower survival than status 4 (P < 0.001). Novel multivariable prediction models derived with prepolicy data ranked candidates correctly more often than the 6-status rankings (Cox proportional hazards model C-index: 0.76; random survival forest model C-index: 0.74). Objective physiologic measurements, such as glomerular filtration rate, had high variable importance. CONCLUSIONS: The treatment-based 6-status heart allocation system has only moderate ability to rank-order candidates by medical urgency. Predictive models that incorporate physiologic measurements can more effectively rank-order heart transplant candidates by urgency.