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
Authors: 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
Authors: 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