LIVER transplant (LT) allocation policies in the US have undergone several revisions to promote fairness and reduce waiting list deaths. In February 2020, the Organ Procurement and Transplantation Network (OPTN) introduced the acuity circle (AC) policy, replacing region-based allocation with concentric circles measured in nautical miles from donor hospitals. This shift aimed to minimise disparities in illness severity, as measured by Model for End-Stage Liver Disease (MELD) scores, at the time of transplant. However, the AC policy faced criticism for not accounting for population size and density, key factors that influence organ availability.
A nationwide retrospective cohort study was conducted to assess the impact of population size within the AC on waiting list outcomes for patients with acute liver failure (ALF) or chronic end-stage liver disease (ESLD) with a MELD score of 37 or higher. Findings revealed that while overall mortality and dropout rates decreased following AC implementation, patients listed at LT centres in low-population areas faced significantly worse outcomes. Candidates with chronic ESLD listed at centres in low-population areas had 1.7 times higher odds of death or clinical deterioration compared with those in medium-population areas.
In contrast, no such disparities were observed among ALF patients, who benefit from a broader 500-nautical mile allocation radius. This larger sharing area appears to mitigate supply-demand imbalances more effectively than the smaller 150-mile radius used for ESLD candidates. The study also highlighted that low-population centres were less likely to secure organs during the initial match run, exacerbating waiting list mortality.
These findings underline the persistent geographic inequities within the US LT allocation system, even after the AC policy reforms. While broader sharing areas may help reduce disparities, the study stresses the need for further strategies to increase organ supply, including enhancing donation rates, improving organ procurement organisation performance, and advancing preservation techniques. Addressing both allocation and supply issues is essential to achieving a truly equitable LT system.
Reference
Tanaka T et al. US population size and outcomes of adults on liver transplant waiting lists. JAMA Netw Open. 2025;8(3):e251759.
