United Network for Organ Sharing (UNOS) staff members authored and presented several studies at the American Transplant Congress (ATC), held April 29 through May 3 at McCormick Place – Lakeside Center in Chicago. UNOS staff members were primary authors of a total of eight abstracts and coauthored an additional four abstracts. In addition, UNOS’ chief medical officer delivered an invited presentation.
NOTE: Some of these studies were supported wholly or in part by Health Resources and Services Administration contract 234-2005-37011C. The content is the responsibility of the authors alone and does not necessarily reflect the views or policies of the Department of Health and Human Services, nor does mention of trade names, commercial products, or organizations imply endorsement by the U.S. Government.
Below is a listing of studies in which UNOS researchers are primary authors. UNOS staff researchers are indicated with an asterisk.
Redefining pediatric heart Status 1A and 1B criteria: Results of early policy evaluation
Authors: Wida Cherikh, Ph.D.*, Ryan Davies, M.D., Yulin Cheng*, William Mahle, M.D.
The researchers, on behalf of the OPTN Pediatric Transplantation Committee, studied early effects of a policy implemented in March 2016 that changed medical urgency criteria for pediatric candidates (ages newborn to 17) awaiting a heart transplant. The changes were intended to emphasize medical urgency over waiting time in heart allocation for children, thus increasing transplant access for the most medically urgent candidates.
They compared data for pediatric heart listings and transplants for a 15-week time period before and after policy implementation. The number of waitlist additions was nearly identical in both cohorts. Both listings and transplants for the most urgent category (Status 1A) decreased substantially, and both listings and transplants for the other categories (Status 1B and Status 2) increased proportionately. These were intended policy goals.
However, the early data also showed that during the early period after policy implementation, more transplant candidates in urgent statuses received exception scores. This means that their urgency status came not from meeting standard policy criteria, but following application to and approval from a regional review board. Percentages both of listings and of transplants increased markedly for candidates with exception scores, both in Status 1A and 1B. The committee will continue to monitor this trend closely as more data become available.
Even with national sharing, the prospects of a 100% sensitized patient receiving a transplant vary dramatically depending on the precise CPRA value
Authors: Darren Stewart, M.S.*, Anna Kucheryavaya, M.S.*, Dolly Tyan, Ph.D., Howard Gebel, Ph.D., Robert Bray, Ph.D., Nicole Turgeon, M.D.
The kidney allocation system (KAS), implemented in December 2014, greatly increased allocation priority for the most highly immunosensitized kidney candidates – those with a calculated panel reactive antibody (CPRA) of 99 to 100 percent. However, early analyses of the new system suggested that transplant access for these candidates may vary sharply depending on their precise CPRA value. To determine the impact of granular CPRA, the researchers calculated rates of organ offers and deceased donor transplants for these very highly sensitized candidates.
Candidates with CPRA values between 99.5 and 99.6 percent had a markedly higher rate of receiving offers and being transplanted when compared to those with a CPRA at or above 99.9 percent. In addition, transplant and offer rates were significantly lower for very highly sensitized candidates with blood type B.
Given that the existing policy already awards extremely high priority to very highly sensitized candidates, additional allocation priority for those above 99.9 percent CPRA likely would have little effect. Instead, the researchers suggest that transplant programs’ listing practices and consideration of other clinical options might have more benefit. These may include a close review of specific antigens listed as unacceptable, greater consideration of offers with a high kidney donor profile index (KDPI) value, and desensitization (either alone or in combination with kidney paired donation).
The benefits of pancreas after kidney (PAK) transplantation
Authors: Michael Curry, M.S.*, Jonathan Fridell, M.D., Jon Odorico, M.D.
Some clinicians believe pancreas after kidney (PAK) transplantation has inferior outcomes compared to simultaneous kidney-pancreas (SPK) transplantation. However, some individual transplant centers have reported excellent and comparable outcomes between the two types of transplants. The researchers examined national data from 1995 through 2010 to observe differences between PAK and other forms of pancreas transplantation, and whether receiving a PAK transplant is more beneficial than remaining on the transplant waiting list.
For uremic transplant candidates, receiving a PAK transplant offered a survival advantage over remaining on the waiting list without receiving either a kidney or a pancreas transplant. Patient survival was similar between PAK and SPK transplantation. In addition, receiving a PAK improved the length of function for the transplanted kidney.
A new methodology for measuring and monitoring equity in access to deceased donor kidney transplants
Authors: Darren Stewart, M.S.*, Amber Wilk, Ph.D.*, Wida Cherikh, Ph.D.*, Ann Harper, M.P.H.*, Read Urban, M.P.H.*, David Klassen, M.D.*, Erick Edwards, Ph.D.*
The authors developed a novel approach to quantify equitable access for deceased donor kidney transplantation and identify factors most associated with disparity in access. The framework of the study will help the transplant community better assess the merits of alternative policy proposals in the future.
The researchers performed regression analysis to predict time to deceased donor kidney transplantation based on 15 individual candidate characteristics, separately for each quarterly time period from January 2010 through March 2016. The kidney allocation system (KAS) implemented in late 2014 appears to have markedly improved equity in access for kidney transplant candidates. Even with overall improvement, however, remaining disparities are largely attributable to differences in the Donation Service Area where the candidate is listed, as well as the candidate’s CPRA and blood type.
One-year graft and patient survival of deceased donor kidney transplants under KAS
Authors: Amber Wilk, Ph.D.*, Darren Stewart, M.S.*, Mark Aeder, M.D., Anna Kucheryavaya, M.S.*, David Klassen, M.D.*
The researchers compared seven-month transplant cohorts before and after KAS implementation to examine the policy’s effect on patient and graft survival for various donor and recipient characteristics.
Overall patient and graft survival rates were lower, but not significantly different, after KAS compared to before KAS implementation. When stratified by donor and recipient characteristics, graft survival decreased significantly for recipients who received a kidney with a KDPI score less than 85, and patient survival decreased significantly for those who had been on dialysis for 10 or more years prior to getting a transplant. Further analysis is needed as more data become available, since early trends in outcomes may be influenced by continued tapering of bolus effects in recipient characteristics.
HOPE Act – the first year
Authors: Amber Wilk, Ph.D.*, Sarah Taranto*, Read Urban, M.P.H.*, David Klassen, M.D.*
The HIV Organ Policy Equity Act (also known as the HOPE Act), implemented in November 2015, allows research on transplantation of kidneys and livers from HIV-positive donors into HIV-positive candidates. The study’s authors reviewed details of donation and transplantation within the first year of implementation.
Nineteen transplants occurred within the first year at four transplant hospitals participating in research protocols, using organs from seven deceased donors. The authors noted a potential disincentive for OPOs to recover organs from HIV-positive donors, given that the maximum number of organs that could be transplanted per donor is three. However, they anticipate that transplants under the HOPE Act may increase in the future as additional data becomes available on the safety and efficacy of transplantation from HIV-positive donors.
Factors associated with death or transplant in low-MELD patients
Authors: Ann Harper, M.P.H.*, Erick Edwards, Ph.D.*, Julie Heimbach, M.D.
The Model for End-Stage Liver Disease (MELD) formula is used to assess liver transplant urgency for candidates age 12 and older. While previous research has not shown a net transplant benefit (survival from transplantation exceeding survival without a transplant) for candidates with a MELD score below 15, some candidates with low MELD scores either die or receive a transplant. The researchers performed regression analysis to identify factors most associated with either death or transplantation among candidates with a MELD score less than 15.
The factor most often associated with waitlist death among these candidates was having encephalopathy (disease affecting brain function, which can be related to liver dysfunction). Low-MELD candidates were markedly more likely to receive a transplant if they had received a MELD exception score for having hepatocellular carcinoma, a form of liver cancer. Further analysis of these comparative risks may lead to better prioritization of people in need of liver transplantation.
Rates of lost to follow-up among pediatric heart, kidney, and liver transplant recipients
Authors: Wida Cherikh, Ph.D.*, Sharon Bartosh, M.D., Read Urban, M.P.H.*, William Mahle, M.D., George Mazariegos, M.D., Eileen Brewer, M.D.
As pediatric transplant recipients (ages newborn to 17) become adults, they typically transition follow-up care to transplant programs serving adults. Some recipients, however, are reported as lost to follow-up (LTF) during this transition period. The researchers, on behalf of the OPTN Pediatric Transplantation Committee, examined rates of LTF reporting for pediatric heart, kidney and liver recipients transplanted over a 10-year period.
LTF rates differed by organ type and by the age range of recipients at the time of transplant. The highest rate of LTF 10 years from transplantation was among adolescent and young adult kidney recipients, perhaps because their follow-up care may transfer more often to an adult nephrologist not affiliated with a kidney transplant program. The lowest LTF rate was seen in the youngest age group of heart recipients.
The researchers emphasize the importance of reporting accurate, long-term follow-up data to better estimate long-term transplant survival. The Pediatric Transplantation Committee continues to work on educational and outreach strategies to improve follow-up reporting, particularly as pediatric recipients transition into adulthood.
David Klassen, M.D., UNOS’ Chief Medical Officer, will deliver a presentation as part of an ATC panel discussion: “The OPTN COIIN project: Early data from a new approach to program oversight” at 5:30 p.m. Monday, May 1. The presentation will describe the COIIN project and feature project metrics and early data from the first cohort of 19 participating centers.
About UNOS and the OPTN:
United Network for Organ Sharing (UNOS) serves as the Organ Procurement and Transplantation Network (OPTN) by contract with the U.S. Department of Health and Human Services, Health Resources and Services Administration, Division of Transplantation. The OPTN brings together medical professionals, transplant recipients and donor families to develop organ transplantation policy.