JAMA
October 12, 2026 · via Europe PMC
Development and Validation of an Adult Medical Urgency Score for US Donor Heart Allocation.
Lyden GR, White M, Ahn DJ, +10 more, Parker WF.
AI summary — for doctors, generated from the abstract only
A medical-urgency score for US donor heart allocation discriminated waitlist mortality better than the current 6-status system, but a simulated match run showed worse early outcomes for the top-ranked candidate.
What was studied
Registry-based observational study of all adult US heart transplant candidates from January 2019 to August 2025, split into training (n = 21 859), validation (n = 7897) and test (n = 8256) sets. A marginal structural model of 6-week mortality without transplant (US-CRS) was built, compared with seven other models, and converted into an allocation policy tested in a match-run simulation of 45 530 donor hearts.
Key findings
- The chosen US-CRS model used 5 laboratory values and 4 therapeutic devices; in test data its mean time-dependent AUC was 0.807 versus 0.693 for the current 6-status system.
- In the match-run simulation, 67% of transplant recipients moved down in rank order under a US-CRS-based system.
- Observed 6-week transplant-censored mortality for the first candidate on the match run rose from 11.2% (95% CI 10.1%-12.5%) to 15.7% (95% CI 13.9%-17.6%).
Clinical relevance
Offers a more objective, physiology-based way to rank heart candidates that is less open to gaming, and it prioritised sicker candidates with higher mortality without transplant. Policy makers must weigh this against the shift in who receives hearts.
Who should care
Limitations
Retrospective registry data with simulated rather than real allocation, so downstream effects on post-transplant outcomes and waitlist behaviour are not shown in the abstract. Findings apply to the US system.
A data-driven urgency score separates risk better than the current statuses, but adopting it would reorder the waitlist substantially and needs careful policy evaluation.
This is an AI-generated summary of the published abstract, not a clinical recommendation. It may not reflect the full text or subsequent updates — verify against the original source before acting on it.
Abstract
Importance
One in 5 heart transplant candidates in the US die or are delisted without transplant. Donor hearts are currently allocated by a 6-status therapy-based system criticized for limited risk stratification and susceptibility to gaming.
Objective
To develop a new heart allocation policy based on an objective medical urgency score that ranks candidates based on the interaction between physiology and mechanical circulatory support.
Design, setting, and participants
Registry-based observational study using data from the US organ transplant system. All adult (aged ≥18 years) heart transplant candidates from January 2019 to August 2025 were included, split into training (2019-2023), validation (2023-2024), and test (2024-2025) datasets.
Main outcomes and measures
A marginal structural model of 6-week mortality without transplant was estimated (the US Candidate Risk Score [US-CRS]). Eight models were compared in held-out data by weighted time-dependent area under the curve (AUC) and calibration by status. Finally, US-CRS was converted into an allocation policy and a match-run simulation of waitlist reordering was performed compared with the current 6-status system.
Results
Adult heart transplant candidates were partitioned into consecutive training (n = 21 859), validation (n = 7897), and test (n = 8256) datasets (mean [SD] age, 53 [13] years; 74% male). The chosen US-CRS model included 5 laboratory values and 4 therapeutic devices (durable left ventricular assist device, intra-aortic balloon pump, microaxial flow pump, and advanced mechanical circulatory support). In test-set cross-sections of candidates actively waiting on the same calendar date, US-CRS had similar or significantly higher time-dependent AUC than the current 6-status system (mean AUC, 0.807 vs 0.693, respectively) and acceptable calibration by status, especially for candidates who received their status by exception. In match-run analysis (n = 45 530 donor hearts), a US-CRS-based system led to 67% of transplant recipients moving down in rank order and increased observed 6-week transplant-censored mortality for the first candidate on the match run from 11.2% (95% CI, 10.1%-12.5%) under the current system to 15.7% (95% CI, 13.9%-17.6%) under the US-CRS-based system.
Conclusions and relevance
In this registry-based study of US heart transplant candidates, a US-CRS-based allocation system prioritized sicker candidates with higher mortality without transplant compared with the current medical urgency statuses.
DOI
10.1001/jama.2026.17403
PMID
42862588
Research metadata (titles, abstracts, authors, publication dates) is sourced from Europe PMC, which aggregates content from PubMed/MEDLINE, PubMed Central, and other providers under the U.S. National Library of Medicine (NLM/NCBI). NLM does not claim copyright on abstracts; the original journal publishers or authors may hold rights to the full articles. AI-generated summaries are derived only from the abstract, never the full text, and are always labeled as AI-generated.
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