Mortality, dropout risk higher on liver transplant waitlist in low-density areas
Key takeaways:
- The acuity circle-based transplant system generally improved LT waiting list mortality and dropout rates.
- Patients waiting for a LT in a low population size area were more likely to experience mortality/dropout.
Critically ill patients with a high MELD score who were waitlisted for liver transplant at centers in low-population areas were more likely to die compared with patients listed in more populated regions, according to JAMA Network Open data.
“While the findings may not directly influence day-to-day clinical decisions, they are highly relevant at a policy level,” Tomohiro Tanaka, MD, MPH, clinical associate professor of internal medicine in gastroenterology and hepatology at University of Iowa, told Healio.
In February 2020, the Organ Procurement and Transplantation Network (OPTN) switched from a region-based system to an acuity circle (AC)-based system to make organ distribution more equitable and address geographic inequities. However, experts have criticized the AC policy for failing to consider population size and density.
This inspired Tanaka and colleagues to perform a U.S. nationwide retrospective cohort study using data from the OPTN Standard Transplant Analysis and Research file to investigate the association between population size around LT centers and waiting list outcomes for patients with chronic end-stage liver disease and high MELD scores or status 1A acute liver failure.
The study included 10,486 adults aged 18 years or older (mean age, 48.5 years; standard deviation, 7.1 years; 60.5% men; 58.1% white) who were first-time waitlisted candidates for deceased donor LT between June 2013 and May 2023 and followed through June 2023. Of them, 6,142 participants (high MELD score, n = 4,561; ALF, n = 1,581) joined the waitlist before the AC system was implemented and 4,344 (high MELD score, n = 3,595; ALF, n = 749) joined after.
Tanaka and colleagues classified the population size as low, middle or high tiers within the AC around each LT center, using radii lengths based on AC allocation policy of 150 nautical miles for participants with a MELD score of 37 or greater and 500 nautical miles for participants with ALF.
Overall, the researchers found that AC implementation lowered waiting list mortality and dropout rates due to clinical deterioration and improved receipt of LT, but its effectiveness varied by population size.
For example, in the high-MELD group, the 30-day mortality/dropout rate for the middle population size group fell from 22% before AC implementation to 12.1% after AC implementation, and LT rates improved from 75.5% to 85.5%. In the low population size group, the 30-day mortality/dropout rate fell from 20.8% to 16.5%, and the LT rate improved from 76.2% to 81.3%.
Despite these general improvements in the high-MELD group, results of a generalized linear mixed-effect model adjusted for demographic and clinical factors showed patients listed at low population size centers were more likely to die before receiving a LT after AC implementation than those in the middle population size group (adjusted OR = 1.68; 95% CI, 1.14-2.46). This difference did not occur when comparing rates prior to AC implementation.
These findings were supported by Fine-Gray competing risk survival regression models, which showed the low population size group had a greater risk for mortality/dropout following AC implementation (subdistribution HR = 1.63; 95% CI, 1.28-2.01).
The researchers reported no significant differences when comparing the high and middle population size centers.
Lastly, each doubling of population size was linked to a 34% reduction in odds of mortality or dropout for the high-MELD group (aOR = 0.66; 95% CI, 0.49-0.9), according to sensitivity analyses.
“Although we did anticipate geographic disparities based on prior simulation studies, it was surprising to observe how stark the negative effect size was for patients with high MELD scores in less populated areas – for example, an odds ratio of 1.7 for mortality or dropout,” Tanaka told Healio.
The ALF cohort, however, showed no significant differences in waiting list mortality or dropout risk related to population density.
The researchers noted several limitations to this study, including its retrospective nature and relatively small sample size.
“Our study highlights the need to advocate for changes that address not just geographic distance, but also the actual donor potential within a given area — an element that should be incorporated into the ongoing development of the continuous distribution framework,” Tanaka told Healio.
Future research should continue to evaluate the transplantation framework utilizing simulation-based modeling to further elucidate the role population size and density play in determining its efficiency, he added.
For more information:
Tomohiro Tanaka, MD, MPH, can be reached on X at @iowa_tanaka.
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