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Many advances have been made in the field of organ transplantation over the years, and lung transplantation rates are showing an upward trend.
Consider statistics. Since 2011, lung transplant rates have increased by 148.3%, reaching more than 258 lung transplants per 100 patient-years. Scientific registry of transplant recipients. U.S. hospitals will perform 2,743 lung transplants in 2022 and 3,049 in 2023, a record high for lung transplants, said Cleveland Clinic pulmonologist Dr. Mariam Varapour, a member of Congress. speak
Still, more than that, Number of adult patients: 4,200 The number of people on the lung transplant waiting list in the United States has remained stable since 2011. Opportunities remain to improve access to candidates who are difficult to match due to biological factors such as height or blood type.
Introducing alternative scoring systems
Valapour collaborates with researchers at the Cleveland Clinic and Case Western Reserve University in Cleveland, Ohio to design a new scoring system that can increase equity in organ transplants, increase transplant rates, and improve survival rates and verified. Their alternative scoring system focuses on blood type and height, two characteristics that are biological shortcomings of today's composite apportionment scores (CAS).
Alternative scoring systems use empirical models to generate a candidate's expected daily donor supply, taking into account the candidate's diagnosis and unique combination of height and blood type. “Since daily donor supply is inversely proportional to biological disadvantage, we converted it into a point scale that can be used to calculate CAS to represent how difficult or easy it is for a candidate to receive a transplant,” Vallapur said. he said. Co-senior author of this book the study.
The team then performed a simulation analysis using the Computational Open Source Model for Transplant Evaluation (COMET) to examine the potential impact of adopting this score in the lung transplant population. COMET will begin by creating a “realistic synthetic population of organ donors and lung transplant candidates” based on data from across the United States, said co-author Johnny Rose, M.D., a scientist at Case Western Reserve University. explained.
“This allows us to simulate the impact of different allocation rules on important outcomes such as transplant volume, number of deaths on the waiting list, and post-transplant survival.”
Differences from the proposed model
Supply-adjusted CAS aims to address the current allocation rules for CAS that create inequities for lung transplant candidates.
“Our lung transplant physician team members recognize that the current points system, designed to assist patients facing biological challenges in receiving a transplant, is inadequate for certain groups. I realized that,” Varapour said.
Part of the question is how CAS independently assesses the effects of blood type and height. Instead, the team's proposed approach simultaneously takes into account disparities based on blood type and height, providing a more holistic view of biological shortcomings.
“Our approach allocates points in a way that directly reflects each candidate's donor organ supply, based on the combined effect of each candidate's unique combination of height and blood type,” Varapur said. added.
Simulation modeling then allowed the researchers to “upgrade existing scoring schemes in place in today's lung transplant policy from points assigned to height and blood type to points derived from a supply-based scoring algorithm.” We were able to compare it with alternative policies to replace it,” Varapour added.
As a result, they predict, the number of transplants will increase and deaths on the waiting list will be subject to hypothetical rule changes.
Addressing inequality
In fact, lung transplant candidates must be matched with a donor of similar height and blood type. But when researchers looked at these biological factors, they found that shorter candidates did not receive as many transplants as taller candidates. Size is an important factor, as candidates for lung transplants need donor lungs that are appropriately sized for their height and fit within their chest cavity.
“Candidates who are 5 feet 9 inches tall are 61% more likely to have access to a transplant compared to candidates who are 5 feet 3 inches tall,” Varapour explained. “This problem is especially pronounced among women, who tend to be shorter than men (for example, 25% of women in the United States are under 5'3, compared to just 1% of men). This is the central mechanism behind the gender differences that have been observed for many years. lung transplant”
Another potential drawback is blood type. Candidates with type O blood can only accept organs from type O donors, but type O organs are compatible with candidates with any ABO blood type. After controlling for height and patient medical urgency, the researchers found that under the current system, type O candidates had a 37% lower transplant rate than type A candidates. “This means that type O candidates face the unique challenge of having to compete with candidates of all blood types for rare organs,” Vallapur added. .
Height and blood type are part of a larger debate about what it means to provide equitable health care, traditionally focused on disparities between gender, race, and socio-economic status. I'm here. “Our scoring system aims to reduce the complex biological barriers that candidates face when receiving a transplant, ensuring that candidates with comparable disease have equal access to transplantation. We are getting closer to that goal,” Varapour said.
“Furthermore, this supply-based scoring approach could help correct long-standing inequalities in lung transplant access for women in the United States and promote a more equitable system for all candidates.”
Proposing scientifically verified solutions
The research team's involvement in clinical practice, policy development, and research regarding lung transplantation enables a holistic understanding of the field.
Next, researchers will present this analysis as an alternative scoring system to be considered in the U.S. lung allocation system, Valapour said. “We continue to investigate ways to improve our understanding of risks and outcomes, including the impact of delayed access to transplants, with the ultimate goal of improving timely access and survival for lung transplant patients. I'm going.''
This project received funding from the National Heart, Lung, and Blood Institute of the National Institutes of Health (R01HL153175).
Vallapur and Rose had no financial conflict to disclose.
