An equitable solution for lung transport candidates

Lung transplantation word cloud illustration

A new study published in the Journal of Heart & Lung Transplantation revealed significant bias still exists in lung transplant access. Researchers from Cleveland Clinic and Case Western Reserve University (CWRU) proved this by examining data of U.S. adult lung transplant candidates and donors. They then used the analysis to create a new method that would improve access for lung transport candidates who are more difficult to match due to their height and/or blood type.

Currently, in the United States, candidates for lung transportation are ranked using a Composite Allocation Score. This measurement includes a biological disadvantage subscore — which considers additional data points for individuals with shorter stature and/or a rare blood type — that is meant to equalize access for disadvantaged patients.

Candidates with type-O blood are at a disadvantage because they can only accept organs from type-O donors, while type-O organs are compatible for candidates of any ABO blood type. Controlling for height and patients’ medical urgency, the study found that type-O candidates had a 37% lower rate of transplant compared with type-A candidates under the present-day system. 

Another critical consideration for surgical feasibility in lung transplantation is the height difference between candidate and donor. There is a well-known comparative shortage of very tall and very short donors. For example, a candidate who is 5’9” has a 61% higher likelihood of accessing a transplant compared with a candidate who is 5”3.”

“This is a central mechanism for the long-observed sex disparity in lung transplant, as women tend to be shorter in stature than men, e.g., 25% of women are 5’3” or shorter compared to only 1% of men,” said Maryam Valapour, MD, MPP, a pulmonologist at Cleveland Clinic, in a press release.

Unfortunately, the current Composite Allocation Score considers the effects of blood type and height independently, making it inconsistent and insufficient in achieving equitable access to transportation. 

The research team's novel approach considers the two disparities simultaneously, thus providing a more holistic evaluation of biological disadvantage, as candidates can have any combination of these biological characteristics. 

For any lung transport candidate, the alternative scoring system projects the supply of compatible organs based on the individual’s combined characteristics. The researchers developed and validated the simulation model to determine the impact of implementing their proposed solution for U.S. patients who are on the lung transport waiting list.

“This approach may result in decreased organ waitlist mortality and increased transplant rates overall,” said Dr. Valapour, who was co-senior author of the study with Jarrod Dalton, PhD, of Lerner Research Institute at Cleveland Clinic.

Dr. Dalton added, “It also better mitigates the compounding biological disadvantages stemming from hard-to-match combinations of blood type and height.” 

Next, researchers will work on optimizing the weighting given to biological disadvantage Composite Allocation Score components. Eventually, this approach could be applied to allocation of other transplanted organs. 

This project was funded by the National Heart, Lung and Blood Institute of the National Institutes of Health (R01HL153175). 

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