COMET-Lung

The model

What is COMET-Lung?

The Computational Open-source Model for Evaluating Transplantation (COMET)-Lung is a computer simulation model allowing for the comparison of outcomes under alternative U.S. lung transplant allocation policies. The model is used by researchers to understand the implications of real and hypothetical policy changes on outcomes such as:

• The number of candidates expected to receive transplants
• The number expected to die while still on the waiting list
• How long candidates will wait for transplants
• How far donor organs will travel to be transplanted
• The rate at which candidates will die following transplant

The model allows for comparison of these outcomes across subgroups defined by demographics, diagnosis, disease acuity, location, and other candidate characteristics. Interested researchers may explore the scientific articles describing and utilizing COMET-Lung and may download the underlying model code for use in their own research at the COMET-Lung GitHub repository.

These simulations use synthetic populations. For the approach to generating these populations, see Creating synthetic populations in transplantation.

The web application

What is COMET-Lung Online?

COMET-Lung Online provides a lightweight version of COMET-Lung that allows anyone to perform basic experiments with the model through an easy-to-use web application. The app is built for doctors, policymakers, patients, or anyone with an interest in transplant policy and outcomes.

Users run experiments by selecting from among available policy alternatives and optionally changing the weights assigned to various subcomponents used to calculate the Composite Allocation Scores (CAS). Results may be stratified by various candidate or geographic factors, and the outcomes of multiple experiments may be compared side-by-side.

Getting started

How do I use COMET-Lung Online?

The user interface provides basic descriptions and instructions. Select a policy alternative, adjust available CAS weights, and run an experiment. You can then explore outcomes by candidate or geographic factors and compare experiments side-by-side.

Understanding the results

How do I know that results from COMET-Lung Online are valid?

Like other simulation models, COMET-Lung is used to explore scenarios that may be impossible to observe naturally—for instance, enacting different policies within the same population over the same period of time.

The model has been tested and shown to accurately reproduce key outcomes under the previous Lung Allocation Score (LAS) allocation system. Similarly, it has been able to accurately predict changes in outcomes stemming from the implementation of the CAS continuous distribution system in 2023.

Models are simplifications of very complex systems, and they may sometimes fail to emulate reality. Your observations about results that seem counterintuitive or contradict real-world experience can help us understand the limitations of the model and improve future versions.