Evolution of out-of-sequence liver allocation, 2019-2024

Area of Science:

• Transplantation Medicine
• Organ Allocation Systems
• Hepatology

Background:

• Allocation out-of-sequence (AOOS) allows deviations from standard deceased donor organ allocation to expedite placement.
• Contemporary practices and impact of AOOS in liver transplantation remain incompletely understood.

Purpose of the Study:

• To characterize current liver AOOS practices, including prevalence, timing, and geographic distribution.
• To examine the association between AOOS and organ utilization and offer acceptance rates.

Main Methods:

• Analysis of liver match runs from 2019-2024 using the OPTN Potential Transplant Recipient dataset.
• Incorporation of Scientific Registry of Transplant Recipients data for program- and OPO-specific utilization analysis.
• Assessment of AOOS prevalence, timing, geographic variability, and correlation with adjusted utilization metrics.

Main Results:

• AOOS allocation increased significantly from 5% in 2019 to 18% in 2024.
• AOOS use was concentrated in specific Organ Procurement Organizations (OPOs) and transplant centers, often geographically linked.
• AOOS offers were initiated earlier in the allocation process over time.
• OPO-level AOOS use did not correlate with donor yield, but center-level AOOS acceptance was linked to higher adjusted offer acceptance.

Conclusions:

• Liver AOOS practices show increasing use and geographic concentration.
• AOOS acceptance by transplant centers may improve organ offer acceptance.
• Further standardization of AOOS practices in liver transplantation is warranted.