San Francisco — United Network for Organ Sharing (UNOS) staff members authored and will present several studies at the World Transplant Congress (WTC), held July 26-31 at the Moscone West Convention Center. UNOS staff members are primary authors of a total of 11 abstracts and are coauthors of an additional 13 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.
Exploring the Candidate/Donor Compatibility Matrix to Identify Opportunities to Improve the OPTN KPD Pilot Program’s Priority Point Schedule
Embargo until Sunday, July 27 – 6:30 p.m. PDT
Authors: Darren Stewart, M.S.*, Ruthanne Leishman, RN, M.P.H., CPTC*, Anna Kucheryavaya, M.S.*, Richard Formica, M.D., Mark Aeder, M.D., Adam Bingaman, M.D., Sommer Gentry, Ph.D., Tuomas Sandholm, Ph.D., Itai Ashlagi, Ph.D.
The OPTN Kidney Paired Donation Pilot Program (KPDPP) arranges matches for living donor kidney transplants from a pool of potential donors and candidates when an intended donor-candidate pair are not biologically compatible. The researchers studied results from the computer algorithm used in the KPDPP to identify the types of patients that are easier or harder to match. They also assessed whether adjustments could be made to generate more matches, especially for patients who are difficult to match.
Candidates with very high immune system sensitization (a CPRA score of approximately 95 percent or higher) were found to be substantially harder to match. They may benefit from a “sliding scale” approach to prioritization, as opposed to the current approach that awards the same number of points for all candidates with a CPRA of 80 percent or higher.
The level of specificity that transplant programs place on matching criteria (for example, whether they would accept a left or right kidney) also affected the number of possible matches generated. Prioritization based on characteristics of donor-candidate pairs (as opposed to candidates only) may increase matching opportunities, as would further increases in the pool of potential donors and candidates entered into the KPDPP.
Improvement in Follow-up Reporting for Living Kidney Donors since Implementation of New OPTN Policy
Embargo until Monday, July 28 – 4:00 p.m. PDT
Authors: Jennifer Wainright, Ph.D.*, Maureen McBride, Ph.D.*, Mary Amanda Dew, Ph.D., Claudine Lougee, B.A.*, Lee Bolton, M.S.N., ACNP*, Christie Thomas, M.B., FRCP, FASN, FAHA
In February 2013, the OPTN implemented minimum thresholds for living donor kidney transplant programs to report clinical and laboratory follow-up data on their donors. This information is important to assess potential donor risk and aid in informed consent for living kidney donation. The researchers studied comparable cohorts of follow-up data before and after the thresholds were established.
National rates of timely clinical data increased from 59.1 percent prior to policy implementation to 65.7 percent after implementation. Timely submission of lab data similarly increased, from 48 percent before implementation to 58.8 percent afterward. Few reports indicated that living kidney donors were unwilling to submit to follow-up. The transplant volume of the individual program was not a factor in the amount of timely reporting; both large and small programs achieved high follow-up reporting rates. Timely reporting should continue to improve as transplant programs continue to learn more about how to meet the new requirements.
4 Years After CPRA: Refusal Due to a Positive Crossmatch Has Declined to 0.4% of Offers
Embargo until Monday, July 28 – 4:48 p.m. PDT
Authors: Anna Kucheryavaya, M.S.*, Gena Boyle, M.P.H.*, Dolly Tyan, Ph.D., Nancy Reinsmoen, Ph.D., Lee Ann Baxter-Lowe, Ph.D.
In October 2009, the OPTN began using a calculated panel reactive antibody (CPRA) formula to assess the likelihood of donor kidneys being biologically incompatible with the recipient. Using CPRA, transplant centers report specific antigens that would be unacceptable for a given candidate, and the formula then estimates the percentage of donors with whom the candidate is likely to be incompatible.
Final compatibility is determined by a “crossmatch” of specific donor and candidate serum samples. A “positive” crossmatch indicates that immune system rejection is highly likely, leading to refusal of the kidney being offered.
The authors examined cohorts of data before and after the implementation of CPRA to determine the effect on the listing of unacceptable antigens and the number of kidney offers refused due to positive crossmatches.
In the four years since CPRA was implemented, the overall percent of kidney offered refused due to positive crossmatches has decreased significantly, from 1.7 percent to 0.4 percent overall. For very highly immunosensitized candidates (those with a CPRA of 98 percent or higher), the rate of offers refused for positive crossmatches decreased even more significantly, and kidneys were transplanted more frequently into the recipients for whom the offer was accepted. Future advances in technology and pending changes to OPTN policy may contribute to further improvements, especially for highly sensitized candidates.
Does Authorization for Donation in the U.S. Vary by Ethnicity?
Embargo until Monday, July 28 – 5:30 p.m. PDT
Authors: Robert Carrico, Ph.D.*, John Rosendale, M.S.*, Dean Kappel, M.S.W., Howard Nathan, CPTC
Authorization for deceased donation varies by a number of demographic criteria. The authors performed generalized linear regression analyses to study the degree to which donor authorization varies between and within ethnicity between among individuals medically eligible to donate.
During a three-year study period, the odds of donor authorization nationwide among potential donors identified as White were 3.9 times greater than Asian, 3.2 times higher than Black, and 2 times higher than Hispanic potential donors. Education and communication both among the staff of organ procurement organizations (OPOs) and with local ethnic communities is essential to optimize donor authorization. The authors identified certain OPOs whose performance in obtaining donor authorization is significantly higher than the baseline for certain ethnic groups; their efforts can inform best practices that may be adopted by others.
That KDPI Is So Yesterday: Analyzing the Impact of Changes in KDPI During the Course of Donor Management
Embargo until Tuesday, July 29 – 12:03 p.m. PDT
Authors: Darren Stewart, M.S.*, Wida S. Cherikh, Ph.D.*, Anna Kucheryavaya, M.S.*, Gena Boyle, M.P.H.*, Richard Formica, M.D., Mark Aeder, M.D.
The Kidney Donor Profile Index (KDPI) will be an integral component of the new kidney allocation system scheduled to be implemented in December 2014. It combines 10 factors about the donor’s medical history and lab values to determine how long a kidney is likely to function once transplanted. The researchers studied how potential changes in the factors affecting KDPI calculation may affect kidney allocation and clinical practice.
For all donors with a kidney recovered for transplantation over a 30-month period, the researchers calculated KDPI and observed whether the score changed for any reason between initial calculation and the time of organ recovery. The KDPI changed at least once for 88 percent of donors, most commonly due to changes in creatinine levels. The degree of change tended to be small for most donors.
Kidneys involving a substantial rise in creatinine level were significantly more likely to be discarded than those with a stable creatinine value. However, graft survival (the rate of continued kidney function) did not differ whether the creatinine level rose sharply or remained stable. This finding suggests that while the terminal creatinine value is a key determinant of donor quality, the creatinine trend prior to donation is not.
A Second Look at the OPTN Explant Pathology Form Data
Embargo until Tuesday, July 29 – 12:27 p.m. PDT
Authors: Ann Harper*, Erick Edwards, Ph.D.*, Kim Olthoff, M.D., Ryutaro Hirose, M.D., Richard Freeman, M.D., Julie Heimbach, M.D.
Approximately 30 percent of liver recipients receive allocation priority due to their having hepatocellular carcinoma (HCC). For these recipients, OPTN policy requires transplant programs to submit post-transplant pathology forms to confirm the HCC diagnosis.
The researchers reviewed more than 2500 forms to determine trends in the stage and characteristics of the tumors. They also studied a subset of recipients to identify potential recurrence of the disease.
More than 90 percent of the recipients who received priority based on HCC status had evidence of an HCC tumor when their native liver was removed. Approximately 71 percent had tumors at stage T1 or T2. A small subset of recipients had disease recurrence. Further study of the characteristics of these recipients, as well as newly available pre-transplant imaging data, may help refine future policy affecting candidates with this form of disease.
A Substantial Increase in Reporting of HLA-DPB Typing of Deceased Donors in U.S.
Embargo until Tuesday, July 29 – 5:30 p.m. PDT
Authors: Anna Kucheryavaya, M.S.*, Dolly Tyan, Ph.D., Gena Boyle, M.P.H.*, David Kiger, CHS, CHT, Cathi Murphey, Ph.D., Lee Ann Baxter-Lowe, Ph.D.
HLA-DPB antigen/antibody typing for transplant candidates is not required by OPTN policy, but data on DPB typing is captured and reported for many deceased donors and transplant recipients. The researchers analyzed the trend in reporting of DPB typing over nearly eight years.
The rate of reporting of DPB typing for deceased donors has increased from 0.1 percent in 2005 to 29 percent in nine months of 2013. The percentage of histocompatibility laboratories reporting such typing has also continued to increase in recent years. These results suggest growing recognition of DPB typing as a useful mechanism to assess donor-recipient compatibility and enhance the efficiency of matching.
Pediatric Kidney Transplant Rates by Sensitization Level after Share 35 Policy
Embargo until Wednesday, July 29 – 11:39 a.m. PDT
Authors: Wida S. Cherikh, Ph.D.*, Jodi Smith, M.D., Harrison McGehee, B.S.*, Chad Waller, M.S.*, Eileen Brewer, M.D.
In 2005, OPTN kidney allocation policy was changed to provide children listed before age 18 local priority for kidneys from deceased donors younger than age 35. The authors analyzed cohorts of data before and after the policy was implemented to assess its effects on transplant rates, especially by candidates’ immune sensitization level (non-sensitized, low sensitized, moderately sensitized or highly sensitized).
Overall transplant rates among pediatric candidates have increased significantly since the policy went into effect, with no offsetting significant change in transplant rates for adult candidates. The transplant rate increased among pediatric candidates whose immune sensitivity ranged from non-sensitized to moderately sensitized. Specifically among candidates with a high level of immune system sensitization, only those age 5 and younger experienced a significant increase in transplant rate.
The OPTN Kidney Paired Donation Pilot Program (KPDPP): Reaching the Tipping Point in 2013
Embargo until Wednesday, July 30 – 4:00 p.m. PDT
Authors: Ruthanne Leishman, RN, M.P.H., CPTC*, Darren Stewart, M.S.*, Catherine Monstello, RRT, CPHQ*, Wida Cherikh, Ph.D.*, Tuomas Sandholm, Ph.D., Richard Formica, M.D., Mark Aeder, M.D.
The authors reviewed progress in the OPTN Kidney Paired Donation Pilot Program (KPDPP) from its launch in 2010 through November 2013. In that time, 133 living donor kidney transplant programs nationwide had agreed to participate in the program, with 92 having entered at least one potential donor-recipient pair for matching.
Transplants arranged through the program increased by 420 percent between 2012 and 2013 (10 and 52 transplants, respectively). This is associated with increases in both the number of matches identified by the system and the match success rate – the proportion of matches that led to a successful transplant (from 3 percent in 2012 to 10 percent in 2013).
Nearly two-thirds of the transplant candidates entered into the matching system had high immune system sensitization (CPRA of 80 percent or above), which greatly limits the possibility of finding a compatible match. Nevertheless, the KPDPP has been very successful in matching these candidates; nearly 30 percent of the recipients transplanted in the study period were highly sensitized. More than one-third of the recipients were ethnic minorities.
The KPDPP is overseen by a work group that continues to work on ways to increase the success rate of matches and provide additional transplant opportunities to candidates through the increasingly successful program.
Two High KDPI Kidneys Are Better Than One: Opportunities To Expand Dual Kidney Transplantation To Reduce Discard Rates
Embargo until Thursday, July 31 – 11:03 a.m. PDT
Authors: Darren Stewart, M.S.*, Wida S. Cherikh, Ph.D.*, Gena Boyle, M.P.H.*, Mark Aeder, M.D., Richard Formica, M.D.
OPTN kidney allocation policies allow transplantation of two kidneys from the same deceased donor if certain medical characteristics of the donor (for example, donor age of 60 or older) suggest a single kidney is less likely to function long-term. Researchers on behalf of the OPTN/UNOS Kidney Transplantation Committee evaluated data on the use of kidneys from these donors to assess whether policy changes may increase organ utilization.
While dual kidney transplantation has decreased in frequency in recent years, it is associated with a substantially lower risk of graft failure than single kidney transplantation for high KPDI kidneys. At the same time, more than 1000 dual kidneys were discarded in 2012 alone from donors with a KDPI above 85 percent. The Kidney Transplantation Committee is studying potential revisions to allocation policy and the matching system to encourage more frequent use of dual kidneys, especially for kidneys otherwise likely to be discarded and for recipients expected to have better survival with these transplants than if they remain on dialysis.
Five-Year Post-Transplant Outcomes of Pediatric Kidney Recipients in the U.S. After Share 35 Policy
Embargo until Thursday, July 29 – 1:39 a.m. PDT
Authors: Wida S. Cherikh, Ph.D.*, Harrison McGehee, B.S.*, Marissa Clark, M.S.*, Chad Waller, M.S.*, Eileen Brewer, M.D.
While an OPTN kidney allocation policy enacted in 2005 has resulted in more pediatric kidney candidates receiving transplants overall, more of these transplants have involved higher antigen mismatches between donors and recipients. Researchers on behalf of the OPTN/UNOS Pediatric Transplantation Committee studied patterns of five-year post-transplant outcomes before and after the 2005 policy.
Despite a higher percentage of pediatric transplants involving antigen mismatches since the policy went into effect, unadjusted graft and patient survival rates were not adversely affected when compared to similar outcomes before the policy change. Other five-year post-transplant outcomes were similar for factors such as treatment for acute rejection, median serum creatinine and retransplant rates. Longer recipient follow-up is needed to assess potential later effects of higher antigen mismatches (especially DR antigen mismatches) on post-transplant outcomes.