Continuous distribution - heart
The heart organ type began work on continuous distribution in August 2022. The Heart 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 2023 public comment in the form of a concept paper. An additional concept paper was available for winter 2024 for public comment.
2. Build framework— in process
The step involves converting the existing heart allocation policy into the new framework through the following exercises and will involve 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 was collected through values prioritization exercises that will help the committee prioritize attributes. The values exercise used a methodology called the Analytic Hierarchy Process, or AHP, and has been used effectively by other healthcare groups to involve patients in making clinical decisions.
All members of the donation and transplantation community, including donors, patients and their loved ones, were encouraged to participate in these important values exercises.
Participants in the winter 2024 values exercises were presented with a pair of attributes that will be used to prioritize candidates. Participant were asked to decide, if all else is considered equal, which of the two attributes is more important than the other when prioritizing a candidate for an organ.
The heart values prioritization exercise was through March 19, 2024. Learn more about the values exercises.
Converting attributes into points
For each attribute that will be factored into the overall score, the Heart 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 adult statuses 1 or 2? Pediatric statuses 1B or 2?
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 hearts, 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 tool for liver is pending release. A similar sensitivity tool will be released following the 2024 heart prioritization exercise.
Developing the composite score
Developing the composite score involved a combination of decided weights and rating scales. Among other resources, the committee will utilize analyses from mathematical optimizations to assist in this step.
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 heart organs proposal – expected 2025
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 heart 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