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UNOS Researchers Present Studies at American Transplant Congress

Boston – United Network for Organ Sharing (UNOS) staff members authored and will present numerous studies at the American Transplant Congress (ATC), held June 11-15 at the John B. Hynes Convention Center. UNOS staff members are primary authors of a total of 19 abstracts and are coauthors of an additional three abstracts.

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.

Characteristics Independently Associated with Kidney Candidates Having CPRA of 99-100%
Embargo until Saturday, June 11 – 5:30 p.m. EDT
Authors: Anna Kucheryavaya, M.S.*, David Klassen, M.D.*, Darren Stewart, M.S.*

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. The researchers studied clinical and demographic characteristics of candidates with a CPRA of 99 to 100 percent just prior to KAS implementation, to identify characteristics most commonly associated with this group of people, as these candidates received increased transplant access under KAS.

The greatest influence on having a CPRA of 99 to 100 percent was having received a prior transplant, with an even greater likelihood among recipients of two or more previous transplants. Other highly significant factors included female gender and whether the candidate was waitlisted at multiple transplant programs.

Survey Results Show Strong Support for Allowing Patients Undergoing Desensitization to Keep Their Pre-Desensitization CPRA Allocation Priority
Embargo until Saturday, June 11 – 5:30 p.m. EDT
Authors: Anna Kucheryavaya, M.S.*, Robert Bray, Ph.D., Dolly Tyan, Ph.D.

Currently, highly immunosensitized kidney candidates who undergo desensitization would lose allocation priority associated with a previous calculated panel reactive antibody (CPRA) value if they no longer have certain unacceptable antigens. A workgroup representing multiple OPTN/UNOS committees conducted a survey of kidney transplant programs and histocompatibility laboratories to seek their views on whether candidates should keep their priority for pre-desensitization CPRA values.

Eighty-five percent of respondents expressed support for having candidates keep pre-desensitization priority under certain conditions. This finding may support assessment of future policy initiatives.

No Significant Impact of KAS on Prior Living Kidney Donors’ Access to Timely Transplant of High Quality Kidneys
Embargo until Saturday, June 11 – 5:30 p.m. EDT
Author: Jennifer Wainright, Ph.D.*, Anna Kucheryavaya, M.S.*, Mark Aeder, M.D., David Klassen, M.D.*, Darren Stewart, M.S.*

Prior living donors who later need a deceased donor kidney transplant receive very high allocation priority. The authors studied cohorts of data prior to and after the implementation of the kidney allocation system (KAS) to investigate whether the system has affected prior living donors in terms of waiting time to transplant or KDPI values of the kidneys they receive. (The Kidney Donor Profile Index [KDPI] is a formula that estimates the potential longevity of donor kidneys based on medical criteria.)

Neither transplant rates for prior living donors, nor median waiting times to transplant, changed significantly after KAS implementation. While the median KDPI value increased moderately after KAS, prior living donors as a group continue to receive kidneys with substantially longer estimated function than the average recipient.

Are Prior Living Kidney Donors with ESRD being Listed and Receiving Transplantation Priority in a Timely Manner?
Embargo until Sunday, June 12 – 3:42 p.m. EDT
Authors: Jennifer Wainright, Ph.D.*, Anna Kucheryavaya, M.S.*, David Klassen, M.D.*, Darren Stewart, M.S.*

Prior living donors who later need a deceased donor kidney transplant receive very high allocation priority. To be listed for this priority, transplant programs must submit a request to the UNOS Organ Center. Any delay in a program’s submission may delay timely access to transplantation. The authors studied OPTN and CMS data to examine the timing of priority requests for prior living donors over a 67-month period.

While most prior living donors received priority and were actively listed for a transplant in a timely manner (more than 40 percent before beginning dialysis), a substantial number spent considerable time either actively listed for a transplant without additional living donor priority or listed in an inactive status. This, in turn, affects their access to timely transplantation. The authors note the need for increased awareness of the benefit of timely listing and understanding of the process for obtaining priority based on prior living donation.

Understanding the Drivers behind an Early Post-KAS Rise in Delayed Graft Function (DGF) Rates
Embargo until Sunday, June 12 – 4:30 p.m. EDT
Authors: Darren Stewart, M.S.*, Anna Kucheryavaya, M.S.*, David Klassen, M.D.*

In the first six months since KAS implementation, delayed graft function (DGF) among recipients of deceased donor kidney transplants increased by 22 percent. The researchers performed regression analysis to identify underlying factors associated with the increase.

The largest single factor associated with the change in DGF is the fact that more post-KAS recipients spent a long amount of time on dialysis than in the pre-KAS period. As evidence has shown a bolus effect where substantially more of these transplants occurred soon after KAS but have decreased over time, the national DGF has started to decrease slowly as well. Even so, after accounting for other traditional factors used to model DGF, a residual unexplained effect remains. This issue will be studied further.

The Finances of Broader Sharing of Livers Following “Share 35”
Embargo until Sunday, June 12 – 5:42 p.m. EDT
Authors: Ann Harper*, Erick Edwards, Ph.D.*, Richard Gilroy, M.D., William Chapman, M.D., David Mulligan, M.D., Goran Klintmalm, M.D.

In 2013, the OPTN implemented a policy to increase regional access to liver transplants for high-urgency candidates – those with a score of 35 or higher using the Model for End-Stage Liver Disease (MELD) or Pediatric End-Stage Liver Disease (PELD) formula. As many transplant institutions reported increased costs associated with broader sharing, the researchers surveyed liver transplant programs to seek to quantify these costs. Twenty-eight liver transplant centers provided cost and post-operative data associated with more than 1,000 transplants. Charged cost for organ transportation and overall expenses were strongly correlated with the distance the organ traveled, with median charges increasing stepwise from local transplants to those performed regionally and nationally. Overall charges for recipient care were strongly correlated with the recipient’s post-transplant length of hospital stay and only weakly correlated with his or her MELD score at transplant.

While not representative of all programs or regions, this is the first survey to gather actual data on a large sample of liver transplants. It will provide useful insight into assessing the potential financial impact of sharing livers across greater distances.

Difficult to Place Livers: Implications for Expanding the Donor Pool
Embargo until Sunday, June 12 – 6:00 p.m. EDT
Authors: Erick Edwards, Ph.D.*, Ann Harper*, John Rosendale*, James Eason, M.D.

A key factor in increasing transplantation is to identify missed opportunities, including potentially underutilized categories of donors. The authors identified clinical factors associated with difficult-to-place livers, then compared them to deceased donors over a 16-month period from whom organs were recovered, to see where additional opportunities may exist.

The authors identified six profiles of donors with potentially harder-to-place livers, accounting for nearly 3,300 donors in the study period. As a group, livers from these donors were more likely to be shared outside the local allocation area than from donors not meeting the profiles. While nearly two-thirds of livers in the profiles were not recovered, 30 percent were transplanted. The authors recommend that criteria such as developed for this study be considered in alternative allocation strategies to identify suitable recipients more effectively and increase the potential of organ utilization.

Recipient Outcomes in U.S. Cases of Post-Donation Living Donor Malignancy
Embargo until Sunday, June 12 – 6:00 p.m. EDT
Authors: Amber Wilk, Ph.D.*, Sarah Taranto*, Cameron Wolfe, M.D., Michael Nalesnik, M.D.

The authors studied instances over a 67-month period of recipients of living donor kidney transplants for whom their living donor was reported to have a malignancy post-transplant, in order to assess the recipient’s graft and patient survival and the potential of donor-transmitted malignancy. Of these recipients, the majority were reported to be malignancy-free one year post-transplant, with no apparent donor-transmitted malignancies. In addition, all the recipients in the study period were alive one year post-transplant, and the vast majority continued to have a functioning transplanted organ at one year. Longer term outcomes should continue to be assessed as more data become available.

Pediatric Access to Kidney Transplantation Under KAS
Embargo until Monday, June 13 – 2:30 p.m. EDT
Authors: Wida Cherikh, Ph.D.*, Darren Stewart, M.S.*, Anna Kucheryavaya, M.S.*, Mark Aeder, M.D., and Eileen Brewer, M.D.

The authors studied transplant rates before and after the implementation of the kidney allocation system (KAS) to assess the policy’s effect on transplant access for pediatric candidates (ages newborn to 17).

After an initial six-month period when fewer pediatric transplants were performed, in the next six months overall percentage of transplantation returned to levels similar to the time before KAS implementation. However, the subgroup of recipients age 5 and younger had a sustained pre-KAS decline; further research will examine whether this is a sustained effect of the policy or random variability due to other factors. Importantly, as compared to adult candidates, the post-KAS transplant rate for pediatrics was still about five times higher than it was prior to KAS. In addition, pediatric recipients consistently received kidneys with a low Kidney Donor Profile Index (KDPI) score, which was an intended goal of KAS.

Understanding the Initial Rise in Kidney Discard Rates Observed Post-KAS
Embargo until Monday, June 13 – 2:42 p.m. EDT
Authors: Darren Stewart, M.S.*, Anna Kucheryavaya, M.S.*, Roger Brown*, David Klassen, M.D.*, Nicole Turgeon, M.D., Mark Aeder, M.D.

After KAS was implemented, deceased donor kidney discard rates increased by 10 percent in the first seven months before returning to pre-KAS level for the subsequent four months. The authors conducted regression analysis on cohorts before and after KAS implementation to determine factors associated with these observations.

The initial increase in discard rates appears largely to be associated with a combination of an increase in biopsy findings that raised greater concern with kidney function, as well as a sharp decline in pump preservation of kidneys with a KDPI score higher than 85 percent. Characteristics of the match run unique to KAS appeared not to be associated with increased odds of discard.

Is facilitated pancreas allocation effective?
Embargo until Monday, June 13 – 4:30 p.m. EDT
Authors: Robert Carrico, Ph.D.*, Jonathan Fridell, M.D., Jon Odorico, M.D., Silke Niederhaus, M.D.

The researchers studied how often pancreas transplant programs have used a provision in OPTN policy that allows the UNOS Organ Center to facilitate allocation of a pancreas within one hour of donor surgery only to programs who have a written agreement to receive such offers. (The majority of pancreas transplants are allocated several hours prior to organ recovery from the donor. Facilitated allocation is intended to provide additional opportunity for organ utilization.)

Facilitated allocation has led to progressively fewer pancreas transplants from 2008 to 2014, and a number of programs that volunteered to be considered for such offers have not accepted any. Some pancreas programs seldom import non-local organs for transplant, and a number of the participating programs perform very few transplants. The researchers conclude that facilitated pancreas allocation could be made more effective by developing qualification criteria for participating programs and allowing offers to be made over a longer period of time prior to organ recovery.

How did the new kidney and pancreas allocation systems affect pancreas utilization in the first six-months?
Embargo until Monday, June 13 – 4:42 p.m. EDT
Authors: Robert Carrico, Ph.D.*, Jonathan Fridell, M.D., Jon Odorico M.D., Zoe Stewart, M.D., Ph.D.

Policy changes implemented in late 2014 created new protocols for allocating simultaneous kidney-pancreas (SPK) transplants. The researchers studied six-month cohorts of data before and after the policy was implemented to measure its effect on utilization of deceased donor pancreata and kidneys.

Pancreas recovery rates did not change in the six months after the new policy was implemented, despite an increase in both deceased donation and transplantation. While there has been an increase in SPK transplants at the regional level, the number of local SPK transplants remained essentially the same since SPK transplants are often being performed for candidates further down the match run. The policy appears not to have affected the percentage of kidneys used for SPK transplantation.

Understanding the Dynamics of a Suddenly Plateauing Kidney Waiting List
Embargo until Monday, June 13 – 6:00 p.m. EDT
Authors: Amber Wilk, Ph.D.*, Erick Edwards, Ph.D.*, Darren Stewart, M.S.*

The number of kidney transplant candidates listed nationwide abruptly leveled off close to the time the kidney allocation system (KAS) was implemented. This followed a lengthy and steady increase of registrations. The researchers analyzed patterns of waitlist additions and removals over a period of nearly 16 years before and 11 months after KAS implementation to assess factors affecting the overall size and direction of the waiting list.

The primary issues affecting the plateau appear to be fewer additions of new candidates and more removals around the time of KAS implementation. Given that dialysis time pre-listing is now credited under KAS, it appears that transplant centers have changed their list management practices and are waiting to list candidates until their dialysis time accumulates.

Investigating geographic variation and other factors to understand the recent rise in U.S. deceased donor transplants
Embargo until Tuesday, June 14 – 3:06 p.m. EDT
Authors: Robert Carrico, Ph.D.*, Darren Stewart, M.S.*, Ryan Ehrensberger, Ph.D.*, Brian Shepard*, David Klassen, M.D.*

Increasing transplant volume is a prime strategic goal for UNOS and the OPTN. Significant increases in deceased donor transplantation occurred nationwide in 2014 and 2015, and the increase has been broad-based across most areas of the country. The researchers studied factors associated with this recent trend to inform ongoing efforts to continue to improve transplant opportunities.

Factors associated with increases in deceased donation and transplantation include anoxia as a cause of death, and cardiovascular failure and drug intoxication as mechanisms of death. By contrast, a significant decrease was noted in head trauma as a cause of death resulting in donation.

Latest VCA Statistics in the U.S.
Embargo until Tuesday, June 14 – 3:30 p.m. EDT
Authors: Wida Cherikh, Ph.D.*, Harrison S. McGehee, B.S.*, Christopher Wholley, M.S.A., NRP, CPTC*, L. Scott Levin, M.D., Sue McDiarmid, M.D., M.B.A.

The authors assessed data describing the status of vascularized composite allograft (VCA) transplantation in the United States from July 2014 through November 2015.

As of November 2015, 52 VCA transplant programs had been approved at 24 hospitals. Twenty VCA candidates were added to the waiting list during the study period. Nine candidates were transplanted, and eight were awaiting transplantation at the end of that period.

VCA transplantation, the researchers conclude, is an evolving form of treatment and is still in its infancy. Data are being collected on post-transplant outcomes to further refine VCA policy and ensure patient safety.

99% and 100% CPRA Patients since KAS: A Substantial Increase in Transplants with Strong Evidence of a Bolus Effect
Embargo until Tuesday, June 14 – 4:30 p.m. EDT
Authors: Anna Kucheryavaya, M.S.*, Mark Aeder, M.D., Nicole Turgeon, M.D., David Klassen, M.D.*, Darren Stewart, M.S.*

The kidney allocation system (KAS) greatly increased allocation priority for the most highly immunosensitized kidney candidates – those with a calculated panel reactive antibody (CPRA) of 99 to 100 percent. Research prior to KAS implementation predicted a substantial early increase in transplant rates for these recipients, with a possible gradual decrease over time due to a bolus effect. The authors studied the rates of solitary deceased donor kidney transplants and waitlist registrations for candidates with a CPRA of 99 to 100 percent recipients before and after KAS implementation to determine the policy’s effect.

As anticipated, the transplant rate for CPRA 99-100 percent candidates increased substantially, from 2.3 percent of all transplants pre-KAS to 17.7 percent in the first month after policy implementation. The transplant rate then tapered considerably in the first six-month period post-KAS, to a rate of about 11 to 12 percent in the seven to 10 months after implementation. This supports the prediction of a bolus effect. The number of candidates remaining on the waiting list with a CPRA of 99 to 100 percent has also decreased. Further research will seek to quantify differences between highly sensitized candidates receiving transplants as opposed to those who remain on the waiting list.

Subtype-Compatible (A2/A2B-B) Transplantation under KAS Increases Access 3-Fold for Blood Type B Patients, yet Very Few Candidates are Listed as Eligible
Embargo until Tuesday, June 14 – 4:30 p.m. EDT
Authors: Darren Stewart, M.S.*, Wida Cherikh, Ph.D.*, Anna Kucheryavaya, M.S.*, Christopher Bryan, Ph.D., Nicole Turgeon, M.D., Mark Aeder, M.D.

Among the provisions of the kidney allocation system (KAS) is the ability for transplant programs nationwide to list eligible candidates with blood type B to receive deceased donor kidneys with compatible subtypes of either A or AB blood types. Prior to KAS, this form of matching had been done on a voluntary basis through a policy variance. The authors studied time periods before and after KAS to examine its effect on A2/A2B to B transplantation.

The rate of A2/A2B to B transplants increased five-fold in the early months after KAS implementation, and candidates with blood type B listed as eligible for subgroup matching had a substantially higher transplant rate than type B candidates not listed for subgroup matching. However, the number of these transplants is still small (less than 10 per month nationwide), and relatively few transplant candidates were reported as eligible compared to the number estimated to qualify medically. For this provision of KAS to reach its full potential, the authors suggest, transplant professionals need to be better aware of the benefits of this treatment option and of strategies for reliable and cost-effective medical screening to determine eligibility.

Liver-Intestine Candidates Benefit from National Sharing
Embargo until Tuesday, June 14 – 4:54 p.m. EDT
Authors: Erick Edwards, Ph.D.*, Ann Harper*, Debra Sudan, M.D.

Changes to liver allocation implemented in June 2013 also addressed priority for candidates requiring a combined liver-intestine transplant. The researchers analyzed two-year cohorts of data before and after the policy change to assess its effect on liver-intestine candidates.

Since policy implementation the number of liver-intestine transplants nearly doubled (from 83 before the policy to 154 afterward), the number of candidates listed for a liver-intestine combination increased, and the probability of receiving a transplant was significantly greater. However, the death rate of liver-intestine candidates remained essentially the same. The OPTN will continue to monitor outcomes to gain a greater understanding of the policy’s impact.

Early Post-Transplant Patient, Graft Survival and Rejection Rates under KAS
Embargo until Tuesday, June 14 – 5:42 p.m. EDT
Authors: Anna Kucheryavaya, M.S.*, Darren Stewart, M.S.*, David Klassen, M.D.*

The researchers compared six-month periods of data before and after KAS implementation to examine the policy’s effect on patient and graft survival, as well as treated episodes of rejection. They assessed rates that were both unadjusted, as well as adjusted for a number of clinical and demographic factors.

Unadjusted patient and graft survival rates were no different in the study periods before and after KAS implementation. The rate of treated rejection episodes was significantly higher post-KAS; however, after risk adjustment the difference lost statistical significance. This suggests that the post-KAS increase in rejection rates may be partially due to a change in recipient characteristics. Additional research will be performed to assess more fully the effect of KAS on post-transplant outcomes.

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