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.

Removing administrative boundaries using a gravity model for a national liver allocation system.

Geographic disparities emerged as an increasing issue in organ allocation policies. Because of the sequential and discrete geographical models used for allocation scores, artificial regional boundaries may impede the access of candidates with the greatest medical urgency to vital organs. This article describes a continuous geographical allocation model that provides accurate organ access by introducing a multiplicative interaction between the patient's condition and the distance to the graft by using a gravity model. Patients with the most urgent need will thus have access to organs from farther away, while those in less urgent need may only have access to organs geographically closer. Compared to the previous French liver allocation scheme, the gravity model precluded transplantations for candidates with a Model for End-Stage Liver Disease (MELD) ≤ 14 for decompensated cirrhosis from 10.3% to 0.6%. Death and delisting while on the waiting list at 1 year also decreased from 30.1% to 22.4% for MELD ≥ 35. Waiting list (cumulative hazard ratio (CHR)  0.84 after adjustment) and posttransplant survival improved significantly (hazard ratio = 0.83 after adjustment). This new liver allocation system provides more equitable access to liver transplants and an efficient and safe alternative to administrative boundaries for geographical models in organ allocation.

New French heart allocation system: Comparison with Eurotransplant and US allocation systems.

Graft allocation rules for heart transplantation are necessary because of the shortage of heart donors, resulting in high waitlist mortality. The Agence de la biomédecine is the agency in charge of the organ allocation system in France. Assessment of the 2004 urgency-based allocation system identified challenging limitations. A new system based on a score ranking all candidates was implemented in January 2018. In the revised system, medical urgency is defined according to candidate characteristics rather than the treatment modalities, and an interplay between urgency, donor-recipient matching, and geographic sharing was introduced. In this article, we describe in detail the new allocation system and compare these allocation rules to Eurotransplant and US allocation policies.

Continuous Monitoring of Transplant Center Performance: Different Options for Different Goals.

BACKGROUND: In France, the need for continuous monitoring of transplant center performance has recently become apparent. Cumulative sum (CUSUM) monitoring of transplantation is already been used to monitor transplant outcomes in the United Kingdom and in the United States. Because CUSUM monitoring can be applied by different methods, the objective was to assess and compare the performance of different CUSUM methods for detecting higher than expected (ie, excessive) graft failure rates. METHODS: Data come from the French transplant registry. Lung and kidney transplants in 2011-2013 constituted the control cohort, and those in 2014-2016 the observed cohort. The performance of CUSUM monitoring, according to center type and predefined control limits, was measured by simulation. The outcome monitored was 3-month graft failure. RESULTS: In a low-volume center with a low failure rate, 3 different types of control limits produced successful detection rates of excessive graft failures of 15%, 62%, and 73% and false alarm rates of 5%, 40%, and 52%, with 3, 1, and 1 excess failures necessary before a signal occurred. In a high-volume center with a high failure rate, successful detection rates were 83%, 93%, and 100% and false alarm rates were 5%, 16%, and 69%, with 6, 13, and 17 excess failures necessary before a signal occurred. CONCLUSIONS: CUSUM performances vary greatly depending on the type of control limit used. A new control limit set to maximize specificity and sensitivity of detection is an appropriate alternative to those commonly used. Continued attention is necessary for centers with characteristics making it difficult to obtain adequate sensitivity or sufficiently prompt response.