Continuous distribution - liver and intestine
Work on continuous distribution of these organ types began in December 2021. The Liver and Intestinal Organ Transplantation Committee is following a series of steps as it works to build and implement the framework.
Below you will find more information about what has been involved with each step of the process as well as the status of each step and any results to date.
1. Identify attributes — in process
The committee is considering several attributes before deciding those that would contribute to the overall composite allocation score. The identified attributes will align with NOTA and the OPTN Final Rule. Any attribute that is based in part on a candidate’s location or listing is only permitted to the extent required by another regulatory factor.
The Committee began with the attributes that are in current policy and is considering additional attributes suggested during summer 2022 public comment in the form of a concept paper. An additional concept paper will be released for public comment in early 2023. The committee is regularly updating the community about its progress.
2. Build framework — in process
The step involved converting the existing liver allocation policy into the new framework through the following exercises, and involved community input.
Prioritizing attributes against each other
The specific weight of each attribute determines how much influence each attribute will have toward the overall score.
Community input is collected through values exercises helps the committee prioritize attributes. The values exercises involve a method called the Analytic Hierarchy Process, or AHP, and the public is invited to take part.
Participants in the winter 2023 values exercises were presented with a pair of attributes used to prioritize candidates. Participants were asked to decide, if all else were considered equal, which of the two attributes would be more important than the other when prioritizing a candidate for an organ. Learn more about the values exercises.
Video: Continuous distribution — Demo of the liver values prioritization exercise
Video: Continuous distribution — Factors related to liver allocation
These recordings were developed to support the winter 2023 liver values exercise.
Results: 2023 community VPE feedback (PDF)
Results: Revealed preference analysis for liver (PDF)
Converting attributes into points
For each attribute that will be factored into the overall score, the Liver and Intestinal Organ Transplantation Committee will recommend how to assign points to candidates according to differences in the attribute itself. For example, how many points do we give to blood type A versus AB? 100 miles versus 1,000 miles?
Conducting sensitivity analysis
A sensitivity analysis is an analysis used by statisticians to change a single variable slightly to measure the impact on an outcome. For continuous distribution of livers and intestines, a sensitivity tool will be used to evaluate these variables. For example, if a change is made to the weight of any attribute, the new match run will be shown as the outcome.
Sensitivity tools for lung and kidney were released after their respective prioritization exercises, as well as for pancreas, kidney-pancreas and islets. A similar sensitivity tool will be released following the 2023 liver prioritization exercise.
Developing the composite score
The composite score will be a combination of the decided weights and rating scales.
3. Modeling and analysis
The Scientific Registry of Transplant Recipients (SRTR) will take proposed allocation policies and model them to determine the impact on candidates. These results will be produced in a report to help identify any potential unintended consequences or harmful outcomes for these example groups.
Additionally, mathematical optimization is an opportunity to utilize modeling and machine learning to quickly and accurately predict outcomes by identifying attribute weights that achieve any set of pre-specified outcomes in near real-time. This mathematical optimization helps narrow the window of options to those within the community’s goals.
These results will estimate the benefit of the new proposal and inform any needed improvements.
4. Public comment on policy proposal
This step will involve considering community input, modeling and analysis, and committee project work, as well as proposing a new composite score as a policy proposal for public comment.
- Continuous distribution of livers and intestinal organs proposal – expected 2024
5. Board approval
The Board of Directors will review the proposal, OPTN and SRTR materials, and public comments, and consider the proposal in light of the requirements of the OPTN final rule. If the Board of Directors approves the proposal with the new framework, plans for implementation will begin.
- Board briefing paper – to follow proposal
6. Implementation
Implementation of the policy for liver and intestine allocation is projected to take approximately 12 months due to the range of changes, required education to the community, and expected impact.
- Policy notice – to follow Board approval