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Geography remains primary influence in kidney donor allocation post KAS
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Despite recent changes in the national organ allocation system aimed at getting donor kidneys to individuals who would have the best long-term benefit, geography – where a potential recipient lives – still has a major influence in how organs are distributed, according to a new study.
“The Kidney Allocation System fundamentally altered kidney allocation, causing a substantial increase in regional and national sharing that we hypothesized might impact geographic disparities,” Sheng Zhou, MD, and colleagues from Johns Hopkins School of Medicine and School of Health wrote in an article published in the American Journal of Transplantation.
The researchers looked at the deceased donor kidney transplant (DDKT) rate under the Kidney Allocation System (KAS) from June 2015 to December 2016, and compared that with a pre-KAS period (June 2013-December 2014) using records for over 120,000 adult and pediatric patients in the Scientific Registry of Transplant Recipients (SRTR). They developed a measurement tool called the median incidence rate ratio (MIRR) to determine the influence of a potential kidney recipient’s donor service area (DSA) on receiving a donated kidney.
“In other words, if we consider two random candidates with similar allocation points from two different DSAs and compare the candidate in the DSA with greater access to transplantation to the candidate in the DSA with less access, we get an incidence rate ratio (IRR) for the DDKT rates for this pair of DSAs,” the investigators wrote. “We then calculated the IRRs of all DSA pairs, comparing the higher DDKT rate to the lower DDKT rate. MIRR is the median ratio of DDKT rates over all pairs of DSAs.”
Zhou and colleagues found that the geographic disparities – as measured by the MIRR – “remains severe overall” under the KAS. “Geographic location has a larger impact on DDKT rate than (estimated post-transplant survey scores) at or below the 20th percentile, or 3-year waiting time. This seems to contradict ‘the Final Rule,’ which states that neither place of residence nor place of listing should be a major determinant of access to a transplant,” they wrote.
The KAS uses a scoring system that considers improved longevity of the recipient post-transplant to distribute decreased donor kidneys and was developed in part to provide greater access to candidates with B type blood, the investigators noted. Under KAS, the points a recipient receives while waitlisted are influenced by the Estimated Post Transplant Survival score, waiting time, candidate age, calculated panel reactive antibody score, blood type, and whether the candidate is a prior living donor. “These changes have been accompanied by broader sharing for sensitized candidates, broader sharing for (Kidney Donor Profile Index) over 85, and elimination of local policy variances,” and it has helped to reduce geographic influence, the investigators acknowledged, even though KAS was not designed for that purpose.
Despite that improvement, the researchers say geographic influence is still a major determinant in where and how kidney organs are distributed. “The impact of geography was greater than the impact of factors emphasized by KAS” in the study, they noted. “Despite extensive changes to kidney allocation under KAS, geography remains a primary determinant of access to DDKT.” – by Mark E. Neumann
Disclosure: The study was funded by the National Institute of Diabetes and Digestive
and Kidney Diseases, Grant/Award Number 1R01DK111233-01. The authors list no relevant financial disclosures.
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David Klassen, MD
Zhou and colleagues presented a novel metric with interpretive appeal – the median incidence rate ratio (MIRR) – revealing that the variability in a candidate’s access to deceased donor kidney transplantation, based on donor service area (DSA) of listing, did not change after the kidney allocation system (KAS) was revised in 2014. This is not surprising because KAS was not designed to address geographic disparities, as Zhou and colleagues noted. Similarly, a recent OPTN/UNOS analysis identified DSA as the factor most associated with disparities in access to transplant in the KAS era.
Although geographic disparities remain, kidney distribution clearly broadened with KAS, as the percentage of transplants distributed outside of the recovering DSA rose from 20% to 30%. In many ways, KAS has demonstrated the network’s ability to successfully allocate kidneys over longer distances to improve access for biologically disadvantaged patients on the waiting list and increase equity.
The OPTN Board of Directors approved specific principles governing geographic distribution of all organs and intends to establish a policy framework that ensures the geographic distribution of organs is only constrained based on consistently applied rationale as permissible by the OPTN Final Rule. It is imperative that future policy changes, based on these principles, leverage the lessons learned from KAS to ensure that organ allocation policies more effectively address geographic inequities.
References:
Zhou S. Am J Transplant. 2018;doi:10.1111/ajt.14622.
Stewart DE, et al. Am J Transplant. 2018;doi:10.1111/ajt.14922.
Stewart DE, et al. Am J Transplant. 2016;16(6):1834-47.
Wilk A, et al. Organ Procurement and Transplantation Network Kidney Transplantation Committee Report. April 19, 2017.
Stewart DE, et al. Clin J Am Soc Neph. 2017;12(12):2063-2065.
Paramesh AS, et al. Am J Transplant. 2017;17(8):2139-2143.
OPTN/UNOS Board adopts principles of geographic organ distribution. https://optn.transplant.hrsa.gov/news/optnunos-board-adopts-principles-of-geographic-organ-distribution/. Accessed June 18, 2018.
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