After you join a transplant program, your transplant team must figure out how urgently you need a new lung. They do this using the Composite Allocation Score.

What is the CAS?

The CAS is a number between 0 and 100. The higher the number, the higher your priority for receiving a lung. The score includes both recipient and donor factors which makes the process more personalized, fair and efficient.

This score is used for everyone 12 years and older who are waiting for a lung transplant. It helps doctors decide who needs a transplant more urgently and who is most likely to benefit from one.

Children younger than age 12 are listed either as Priority 1 or Priority 2 based on their current level of illness, which means their scores will look different.

The goal of the Composite Allocation Score is to create a more fair, efficient, and personalized system for allocating donor lungs.

The older system, the Lung Allocation Score, focused mostly on how sick a person was and how well they were expected to do after transplant. While those factors are still important, CAS goes further. It includes additional considerations such as geographic distance from the donor, how hard a person is to match, and efforts to ensure equal access for all patients.

Unlike LAS, which applied the same formula to all adults, CAS adjusts based on each person’s unique situation—helping to better match the right patient with the right lung at the right time.

By combining urgency, expected outcomes, match likelihood, access equity, and logistics, CAS aims to ensure organs are used wisely and reach those who need them most—no matter where they live.

How is the score calculated?

Your transplant team will collect medical information through a series of tests. The score is based on things like:

• Your lung function
• Your oxygen levels
• Your age and body size
• If you use a ventilator
• Whether you have diabetes or kidney issues
• How well you can walk (as in a 6-minute walk test)
• Your right heart pressuers
• How urgently you need a lung transplant
• Distance from the donor hospital to your transplant center
• Your blood type
• Your height
• Whether you have antibodies to certain donors.

Your team will update this information at least every 6 months. If your condition changes, they may update it more often.

What if the score doesn’t reflect your situation?

If your team thinks your score is too low for how sick you are, they can appeal to the Lung Review Board. For pulmonary hypertension patients, the board may increase your score if:

• You are getting worse despite treatment
• Your heart’s right atrial pressure is over 15 mmHg
• Your cardiac index is less than 1.8 L/min/m2

If approved, your LAS may be raised to the 90th percentile – meaning you’ll be closer to the top of the waiting list.