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UNOS Researchers Present Studies at American Transplant Congress

UNOS Researchers Present Studies at American Transplant Congress

Seattle – United Network for Organ Sharing (UNOS) staff members authored and will present several studies at the American Transplant Congress (ATC), held June 2-6 at the Washington State Convention Center. UNOS staff members are primary authors of a total of 20 abstracts and are coauthors of an additional five abstracts. In addition, three UNOS researchers will deliver invited presentations.

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.


Measuring and monitoring equity in access to deceased donor liver transplants

Embargo until Saturday, June 2 – 5:30 p.m. PDT

Authors: Darren Stewart, M.S.*, Amanda Robinson, M.S.*, Ann Harper, M.P.H.*, David Klassen, M.D.*

The Organ Procurement and Transplantation Network (OPTN) recently developed a methodology to measure equity in access to deceased donor liver transplantation, adapted from previous work to study equity for deceased donor kidney transplantation. This approach identifies factors most associated with disparities in the likelihood of waitlisted candidates to receive a deceased donor transplant.

The researchers analyzed data on actively listed liver candidates from January 2010 to September 2017, adjusting for 16 covariates. Intended disparities based on the priorities of the liver allocation system (such as the effect of urgency status and MELD/PELD score) were discounted, so that the effects of unintended disparity factors would be most apparent.

The aggregate measure of disparities has remained relatively stable over time, suggesting the effect of such factors has not greatly increased or decreased during the study period. The Donation Service Area (DSA) of candidate listing was the one most associated with unintended disparity in access, more than doubling the next most common factor (candidate blood type).

This methodology can yield an Access to Transplant (ATS) score based on various risk-adjusted factors. Assessing average ATS by the DSA of candidate listing provides a new means to assess system-level equity in access to liver transplantation, particularly in light of enhancements to liver distribution policy scheduled for implementation late in 2018.

Impact of changes to the LAS calculation

Embargo until Sunday, June 3 – 2:30 p.m. PDT

Authors: Rebecca Lehman, Ph.D.*, Robert Carrico, Ph.D.*, Kimberly Uccellini, M.S., M.P.H.*, Kevin Chan, M.D., Timothy Whelan, M.D.

The OPTN implemented several major revisions in February 2015 to the Lung Allocation Score (LAS), which prioritizes lung transplant candidates by a combination of medical urgency and likelihood of early post-transplant survival.  The researchers studied two cohorts of lung candidates age 12 and older, who were either added to the waiting list or transplanted within the year before and the year after the policy revision, to assess early effects of the changes.

There was a significant increase in one-year post-survival rates associated with the new policy (from approximately 86 percent before implementation to about 89.4 percent afterward).  Of the four diagnosis groups within LAS, the score at the time of listing increased significantly for Group B (pulmonary vascular disease) but decreased for Group D (restrictive lung disease).


EVLP on donor lungs: National trends and outcomes

Embargo until Sunday, June 3 – 2:54 p.m. PDT

Authors: Rebecca Lehman, Ph.D.*, Robert Carrico, Ph.D.*, Kimberly Uccellini, M.S., M.P.H.*, Kevin Chan, M.D., Timothy Whelan, M.D.

Ex vivo lung perfusion (EVLP) involves preserving donated lungs in a machine that allows them to be further treated and evaluated before transplantation. Since April 2015, the OPTN has tracked EVLP usage for deceased donor lungs recovered for transplant. The researchers analyzed data on deceased donor lungs recovered from April 2015 through June 2017 to assess EVLP usage and outcomes.

During the study period, EVLP either was performed or was intended to be performed on 254 donor lungs, representing less than three percent of lungs recovered for transplant in that time.  Of the lungs where machine perfusion was performed or intended, 139 (54.7 percent) were transplanted; some or all of these organs may not have been transplanted without the use of perfusion.  While there was considerable variation in EVLP usage among individual organ procurement organizations (OPOs) nationwide, perfusion was not localized to a particular area of the United States.

Among recipients of EVLP lungs, neither the odds of major graft dysfunction nor one-year patient survival differed significantly from recipients of lungs not on machine perfusion.  Recently the OPTN began collecting additional data on EVLP usage, which may provide more detailed insight in the future.


Transplant hospitals increase volumes and acceptance rates under the COIIN Project

Embargo until Sunday, June 3 – 2:54 p.m. PDT

Authors: David Klassen, M.D.*, Henrisa Tosoc-Haskell, RN, M.S.H.A.*, Kristen Sisaithong, M.A.*, Maureen McBride, Ph.D.*, Michael Curry, M.S.*

The Collaborative Innovation and Improvement Network (COIIN) is a three-year study exploring an innovative approach to transplant performance monitoring and increasing transplantation, particularly focus on utilization of deceased donor kidneys with a kidney donor profile index (KDPI) score greater than 50 percent.  The authors reviewed transplant recipient characteristics for the first cohort of participating transplant programs (a second cohort continues to participate in a current study period).

Through the collaborative, participating centers develop and share practice improvements in candidate evaluation and listing and offer acceptance. Using these approaches, the first cohort of centers experienced increases in offer acceptance rates and transplant volumes, including increased use of kidneys with moderate to higher KDPI values. Patient safety and functional outcomes will continue to be closely monitored.


Two years of the HOPE Act

Embargo until Sunday, June 3 – 3:30 p.m. PDT

Authors: Amber Wilk, Ph.D.*, Christine Durand, M.D., Dorry Segev, M.D., Ph.D., 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 from January 1, 2016, to May 4, 2018.

Within the study period, 54 transplants occurred at transplant hospitals participating in research protocols, using organs from 26 deceased donors initially identified as HIV-positive.  These transplants otherwise would not have been possible without the HOPE Act.  The researchers note the potential underutilization of the act’s provisions, as thus far only 21 OPOs (36 percent) have recovered any donors identified as HIV-positive and only 32 percent of transplant centers participating in research protocols have performed a transplant from an HIV-positive donor.  While data monitoring is ongoing for safety criteria established by the National Institutes of Health, no sentinel safety events were observed during the study period.


Kidney registration volume versus expectation: Impact of ESRD burden and outreach

Embargo until Sunday, June 3 – 4:42 p.m. PDT
Amber Wilk, Ph.D.*, Read Urban, M.P.H.*, Julia Foutz, M.P.H.*, Robert Carrico, Ph.D.*

After the December 2014 implementation of the Kidney Allocation System (KAS), many kidney programs reduced the number and type of candidates they listed for a transplant.  The researchers analyzed kidney and kidney-pancreas registrations for three years surrounding KAS (2012, 2014, 2016) to assess actual versus predicted center registration volume.  They also developed a metric of center community need, comparing candidate registrations with calculated local prevalence of end-stage renal disease (ESRD), to study the relationship between listing patterns and disease burden in the community.

Of the 192 centers performing at least 10 kidney or kidney-pancreas transplants in each of the years studied, there was considerable variation actual versus predicted waiting list registrations, suggesting inconsistency in listing behaviors as a function of community need.  Future analysis will seek input from centers across the range of outcomes to learn more about their approaches to potential candidates and share effective practices for education and listing.


Informed clustering of Donation Service Areas for improved benchmarking

Embargo until Sunday, June 3 – 6:00 p.m. PDT
Authors: Samantha Noreen, Ph.D.
*, John Rosendale, M.S.*, Robert Carrico, Ph.D.*

Each of the 58 organ procurement organizations nationwide has a Donation Service Area (DSA).  Population size and characteristics and land area vary widely among DSAs, making it difficult to compare them in an attempt to characterize one OPO’s performance relative to others.  However, some commonalities may exist.  The researchers examined data from several sources in a partitioning analysis to determine natural associations of DSAs based on common factors.

The analysis revealed ten cluster patterns that account for 62.5 percent of the explained variance among DSAs.  The clusters associate multiple patterns, often combining demographic factors such as ethnicity or population density with clinical factors such as disease prevalence or transplant listings.  Some DSAs that share common factors are geographically contiguous but many are not, suggesting that benchmarking should not be based on proximity alone.


Differences in lost to follow-up events for pediatric and adult kidney recipients

Embargo until Sunday, June 3 – 6:00 p.m. PDT
Authors: Amanda Robinson, M.S.*, George Mazariegos, M.D.
, Sharon Bartosh, M.D., William Mahle, M.D.

While the majority of kidney transplant recipients are followed by their transplant program, many are eventually reported to the OPTN as “lost to follow-up.”  The risk of being reported as lost to follow-up varies by age at transplant but is more common among those aged 12 to 25 at the time of transplant.  The researchers used various source data to identify incidences of death, return to the waiting list or return to dialysis among recipients transplanted over a 6-year period and reported as lost to follow-up within 10 years, with particular attention to younger recipients.

The majority of recipients reported as lost to follow-up could not be identified as having any of the adverse events studied, so they likely continue to have a functioning graft and receive follow-up care.  As a result, long-term patient and graft survival may be underestimated, particularly for younger recipients lost to follow-up but who would be expected to have the longest survival.

Of recipients where an event was identified, adolescent recipients were more likely to return to dialysis that recipients of other age groups at transplant.  In addition, adolescent and young adult kidney recipients were more likely to be relisted for a transplant but less likely to die than recipients transplanted at age 26 or older.


One-year graft survival for longevity-matched kidneys in the post-KAS era

Embargo until Sunday, June 3 – 6:00 p.m. PDT
Amber Wilk, Ph.D.*, Mark Aeder, M.D., Vincent Casingal, M.D., Nicole Turgeon, M.D.

One of the primary goals of KAS was to improve the effectiveness of deceased donor kidney transplantation by more closely matching the projected longevity of the kidney with the projected need for the recipient. To assess this, the researchers analyzed one-year graft survival for kidney recipients in the year following KAS implementation, both by the kidney donor profile index (KDPI) and the recipient’s estimated post-transplant survival (EPTS) score.

These early results suggest that longevity matching is achieving its goal.  As KDPI increased (suggesting a shorter period of expected kidney function), one-year graft survival decreased.  Similarly, as recipients’ EPTS increased (suggesting a shorter-term estimate of post-transplant survival), one-year graft survival also decreased. For combinations of matches based on both higher KDPI and higher EPTS, graft survival decreased proportionally when compared to matches involving low KDPI and low EPTS.   More analysis is needed to understand how other clinical characteristics may interact with KDPI and EPTS to affect kidney graft outcomes.


OPTN vascularized composite allograft (VCA) waiting list trends

Embargo until Sunday, June 3 – 6:00 p.m. PDT

Authors: Jennifer Wainright, Ph.D.*, Christopher Wholley, M.S.A.*, Wida Cherikh, Ph.D.*, Jennifer Musick, B.A.*, David Klassen, M.D.*

The researchers studied trends in the waiting list and transplants for vascularized composite allografts (VCA) from July 2014 through March 2018.

The composition of the VCA waiting list has evolved over time as new procedures have developed.  For example, upper limb and craniofacial candidates accounted for much of the waiting list early in the study period, where more recently uterine and penile transplant candidates have become more common.  Twenty-three candidates received deceased donor VCA transplants within this period, with six more receiving uterine transplants from living donors.  While the median waiting time for upper limb and craniofacial transplants was 161 days, individual waiting times vary considerably.  These activities will continue to be monitored as VCA transplantation continues to evolve rapidly.


Vascularized composite allograft (VCA) deceased donors in the U.S.

Embargo until Sunday, June 3 – 6:00 p.m. PDT

Authors: Jennifer Wainright, Ph.D.*, Christopher Wholley, M.S.A.*, Wida Cherikh, Ph.D.*, John Rosendale, M.S.*, David Klassen, M.D.*

The researchers examined characteristics of all deceased VCA donors reported to the OPTN from 1998 through 2017.  This study represents the most detailed description to date of deceased VCA donors in the United States.

A total of 72 deceased donor VCA transplants were performed.  The most common forms of transplant were upper limb (17 unilateral and 15 bilateral), abdominal wall (19), and craniofacial (13).

The vast majority of VCA donors (86.4 percent) were Caucasian.  Approximately 70 percent were male.  Most donors were between 18 and 54 years old, with a median age of 27.  Donors varied greatly in body mass index and in KDPI, an estimate of likely amount of time a donated kidney would be expected to function.


Upper limb transplantation in the U.S.: An early look at OPTN data

Embargo until Sunday, June 3 – 6:00 p.m. PDT

Authors: Jennifer Wainright, Ph.D.*, Scott Levin, M.D., Christopher Wholley, M.S.A.*, Wida Cherikh, Ph.D.*, David Klassen, M.D.*, Linda Cendales, M.D.

The researchers reviewed recipient characteristics and outcomes for all upper limb transplants reported to the OPTN from July 2015 through April 2018.

Ten people received limb transplantation during the study period (six bilateral and four unilateral transplants).  The majority of recipients were male and Caucasian.  As of the end of the study period, all ten were alive and nine had viable grafts; one was reported with early post-transplant graft loss.  Of those for whom complete reported complication data were available, one recipient had infectious complications; none experienced new-onset diabetes or metabolic complications.  Continued follow-up is needed to determine longer-term survival.


Facial allotransplantation: An early look at OPTN data

Embargo until Sunday, June 3 – 6:00 p.m. PDT

Authors: Jennifer Wainright, Ph.D.*, Scott Levin, M.D., Christopher Wholley, M.S.A.*, Wida Cherikh, Ph.D.*, David Klassen, M.D.*, The researchers reviewed recipient characteristics and outcomes for all craniofacial transplants reported to the OPTN from 2008 through April 2018.

Fourteen people received craniofacial transplantation during the study period.  All were Caucasian and most were male.  Of the 13 who had a reported cause for needing a transplant, eight were due to trauma and five due to burns or explosions.

As of April 2018, all recipients were alive and had intact grafts.  Of those for whom complication data were available, eight recipients had at least one acute rejection episode and four had infectious complications; none experienced new-onset diabetes or metabolic complications.  Continued follow-up is needed to determine longer-term survival.


DonorNet and biases in decision-making: An organ offer simulation study

Embargo until Sunday, June 3 – 6:00 p.m. PDT

Authors: Darren Stewart, M.S.*, Jan Lindemans, Ph.D., Jesse Schold, Ph.D., Harrison McGehee, B.S.*, Judd Kessler, Ph.D., Colin Sullivan, M.A., Megan Turner, M.D., Kristin Mekeel, M.D., Carl Berg, M.D., Robert Stratta, M.D., Richard Formica, M.D., Lloyd Ratner, M.D., David Klassen, M.D.*, Brian Shepard, M.B.A.

To study potential improvements to clinical decision-making using behavioral science, UNOS has developed a simulation of DonorNet (the software application used to make and respond to organ offers) to test variations in how clinicians evaluate hypothetical organ offers.

The researchers recruited 68 kidney transplant surgeons and physicians to evaluate and respond to 20 hypothetical kidney offers with the same clinical data but with variations in displaying the offer sequence number of the candidate and whether other programs had previously refused the offer.

Acceptances for the hypothetical offers varied widely, ranging from rates of 11 percent to 95 percent among individual clinicians.  Remarkably, variation among physicians and surgeons at the same transplant hospital was ten times greater than among those at different hospitals.  The researchers will continue to study behavioral aspects of offer acceptance, including factors viewed as most essential to decision-making.


Increasing use of exceptions after changes to pediatric heart allocation

Embargo until Monday, June 4 – 3:42 p.m. PDT
Authors: Amanda Robinson, M.S.*,
William Mahle, M.D., Ryan Davies, M.D.

In 2016, pediatric heart allocation policy was changed to better align candidates’ medical urgency status with waitlist mortality.  The authors analyzed data on pediatric heart candidates and recipients for comparable periods before and after the updated policy to evaluate patterns of listing, wait list deaths and transplant rates.

Listings for Status 1A (most urgent) candidates decreased and Status 1B (next most urgent) increased, as intended.  However, there was a significant increase in the number of children listed as 1A by exception, who tend to have lower waiting list mortality rates compared to candidates meeting standard listing criteria.  This has likely limited the improvement in transplant rates among other Status 1A candidates.  Further improvement may require behavioral modification in exception requests and approvals or more formal approaches, such as establishing a national review board.


Broader sharing has facilitated increases in transplantation from 2014 through 2017 in the United States

Embargo until Monday, June 4 – 5:30 p.m. PDT
Authors: Bob Carrico, Ph.D.*, Brian Shepard, M.B.A.*
, David Klassen, M.D.*

Deceased donor transplantation has increased at a sustained high pace since 2014.  The researchers compared data from two eras (2009-2013 and 2014-2016) to examine variation in local versus export transplants across donor service areas (DSAs) and see how these trends relate to donation per OPO.

Local volume of deceased donor transplants beginning in 2014 increased by a median of 6.3 percent, while export transplants increased by a median of 38.5 percent.  Many individual OPOs exceeded the national median of increase in exported transplants, including nine of the 10 OPOs that increased their average annual volume of deceased donor transplants the most.


Reliability of bronchiolitis obliterans syndrome (BOS) reporting to the OPTN

Embargo until Monday, June 4 – 6:00 p.m. PDT

Authors: Robert Carrico, Ph.D.*, Rebecca Lehman, Ph.D.*, Kimberly Uccellini, M.S., M.P.H.*, Kevin Chan, M.D., Timothy Whelan, M.D.

Chronic rejection of a lung transplant is traditionally classified as bronchiolitis obliterans syndrome (BOS).  OPTN data requires lung transplant programs to report BOS stage for recipients on follow-up forms.  The researchers studied reporting from 2009 to 2015 to see how often the progression of BOS data meets expected progression of chronic rejection.

The criteria reported often varied for individual candidates, some with expected progression of BOS and some with unexpected trajectories.  Trends indicate that reporting is not consistent within each center or for each patient.  The OPTN Thoracic Organ Transplantation Committee is examining discrete, objective data elements that may better allow detection of chronic lung allograft dysfunction.


Early considerations for deceased donor chains

Embargo until Tuesday, June 5 – 3:06 p.m. PDT
Alice Toll*, Ruthanne Leishman, RN*, Vincent Casingal, M.D., Mark Aeder, M.D., Tuomas Sandholm, Ph.D., Nicole Turgeon, M.D.

The potential use of deceased kidney donors to initiate kidney paired donation (KPD) chains (deceased donor chains) has been of interest to the transplant community. The OPTN Kidney Transplantation Committee created a deceased donor chains work group to begin discussion about possible nationwide adoption of the practice.  To assess potential implications of establishing such chains, the authors compared a cohort of OPTN data on kidney transplant recipients and candidates and deceased kidney donors with OPTN KPD donors using the published living kidney donor profile index (LKDPI), which uses the same scale as KDPI.

While OPTN KPD donors were slightly older than deceased donors, they were of higher quality (median 16 LKDPI vs 51 KDPI). Comparison of the waitlist revealed differences in characteristics related to allocation priority; 22 percent of KPD candidates were listed with a CPRA of 100 percent, compared to 5 percent of non-KPD candidates.  The work group will continue to discuss potential mechanisms for DD chains, such as whether kidneys should be allocated as a part of or outside of KAS, and how to maintain equitable access to the waitlist.


What type of deceased donors do KPD candidates accept?

Embargo until Tuesday, June 5 – 3:42 p.m. PDT
Alice Toll*, Ruthanne Leishman, RN*, Vincent Casingal, M.D., Mark Aeder, M.D., Tuomas Sandholm, Ph.D., Nicole Turgeon, M.D.

OPTN KPD candidates are required to also be listed on the waitlist for deceased donor transplantation, and many leave the program for a deceased donor transplant. Understanding the types of deceased donors those candidates are willing to accept can shape potential development of a deceased donor chains protocol.  The researchers examined data on 352 OPTN KPD candidates who received a deceased donor kidney-alone transplant to determine donor characteristics.

In general, KPD candidates were more likely to accept deceased donors with favorable characteristics (lower age, BMI and KDPI).  They were also more likely to accept donors located closer to their transplant center, even if this involved a higher degree of HLA mismatch.  The deceased donor chains workgroup will consider whether a policy may be developed in light of these acceptance patterns.


ESRD in living kidney donors

Embargo until Tuesday, June 5 – 9:15 p.m. PDT

Authors: Jennifer Wainright, Ph.D.*, Amanda Robinson, M.S.*, Amber Wilk, Ph.D.*, David Klassen, M.D.*, Wida Cherikh, Ph.D.*, Darren Stewart, M.S.*

The authors compared OPTN and external source data on living kidney donors between April 1994 and September 2016 to identify risk factors for developing end-stage renal disease (ESRD) within 20 years.

A total of 218 living donors were determined to have developed ESRD, with a median time of 11.1 years between donation and reported onset. While the 20-year risk is low for many donors, the risk of ESRD varies considerably by certain demographic and clinical factors.  Some univariate factors associated with higher risk include donation to an identical twin or living in an area with lower median neighborhood income.  Combination effects were also noted.  For example, ESRD risk increases with donor age for Caucasian donors, while African-Americans of younger donation age are at greater risk.  Clinicians and donor advocates should consider these findings in terms of more detailed informed consent discussion for potential living donors in increased risk categories.

In addition, the authors note that the 20-year risk horizon calculated within this study does not equate to lifetime risk, since the risk of ESRD onset increases exponentially.  Additional long-term analyses are needed to learn more about cumulative risk.


An early look at the OPTN’s new simultaneous liver kidney (SLK) allocation policy

Embargo until Wednesday, June 6 – 9:15 a.m. PDT
Authors: Anna Kucheryavaya, M.S.*, Richard Formica, M.D.,
Nicole Turgeon, M.D., Darren Stewart, M.S.*, Amber Wilk, Ph.D.*

In August 2017, the OPTN implemented a simultaneous liver-kidney (SLK) allocation policy. It established renal medical criteria for patients waiting for SLK transplants and created new allocation priority (“safety net”) for patients listed for a kidney within a year of liver transplant (KAL) with prolonged renal dysfunction. The researchers compared pre- and early post-implementation results to assess policy performance.

Early results do not indicate any unintended consequences of the policy.  Thus far, the percentage of deceased donor kidneys going to liver candidates has decreased slightly and the average monthly number of SLK transplants has also decreased slightly.  However, these early results should be interpreted with caution. Further monitoring will be performed to allow more definite conclusions about policy performance.


Invited Presentations

June 3, 7:25 a.m.: Wida Cherikh, Ph.D., will present “Current status of VCA in the United States”

June 4, 11:15 a.m.: Robert Carrico, Ph.D., will present “Show me the data – Understanding UNOS data services, benchmarking reports, and CUSUM”

June 5, 7:00 a.m.: David Klassen, M.D., will present “Emerging perfusion technology: Challenges to implementation”


Co-authored studies

UNOS staff members were contributing authors to an additional five studies presented at ATC on behalf of the OPTN Ad Hoc Disease Transmission Advisory Committee:

  • HCV Ab+/NAT- Organ Donors, and the Challenges of ‘Eclipse Windows’
  • Donor-Derived Transmissions in 2016-2017
  • Donor-derived Hepatitis B Virus Infection
  • Don’t Pass the Peanuts: Donor-derived Nut Allergy after Solid Organ Transplantation
  • Outcomes from donors with reports of suspected and proven renal cell carcinomas (RCC)


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.

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