April 29, 2011
UNOS Researchers Present Studies at American Transplant Congress
Philadelphia -- Researchers from United Network for Organ Sharing (UNOS) authored and will present several studies at the American Transplant Congress (ATC), a joint meeting of the American Society of Transplant Surgeons and the American Society of Transplantation held at the Pennsylvania Convention Center April 30 through May 4. UNOS staff researchers are authors in a total of eight papers being presented at ATC. In addition, a UNOS staff researcher will participate in two invited presentations.
Below is a listing of studies and presentations in which UNOS researchers are primary authors. UNOS staff researchers are indicated with an asterisk.
NOTE: Some of these studies were supported wholly or in part by Health Resources and Services Administration contract 234-2005-370011C. 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.
Mining OPTN Data for Opportunities to Place Marginal Organs More Quickly
Embargo until Saturday, April 30 – 6:00 p.m. EDT
Authors: Darren E. Stewart, M.S.*, Kimberly H. Taylor, RN*, Jeffrey P. Orlowski, M.S., CPTC, Phillip A. Camp, M.D., Michael Angelis, M.D., Robert A. Metzger, M.D.
Maximizing the efficiency of organ placement – accepting an organ with the right characteristics for the right recipient – is a major goal of the transplant system. UNetSM, the computer program used for placement of deceased donor organ offers nationwide, allows transplant programs the opportunity to enter detailed criteria on offers they are willing to accept for one or more candidates. In particular, these screening criteria can be used to set specific conditions for a program’s acceptance of extended criteria donor (ECD) kidney offers.
The researchers studied acceptance rates for kidney transplant programs over a period of more than two years to identify whether programs consistently refused organ offers for certain donor characteristics, when instead the centers could have entered criteria into UNet to defer such offers and allow them to be placed more efficiently with programs who may accept them.
More than 70 kidney programs had patterns of organ refusal based on donor characteristics that could have been programmed into UNet for more efficient placement. The researchers recommend sharing these data with transplant programs to improve their screening practices and allow more focused opportunities to place ECD organs quickly for optimal outcomes.
Are Adult Candidates Needing a Combined Liver and Intestine Transplant Disadvantaged in the Liver Allocation System?
Embargo until Sunday, May 1 – 2:39 p.m. EDT
Authors: Erick B. Edwards, Ph.D.*, Ann M. Harper*, Debra Sudan, M.D., W. Kenneth Washburn, M.D.
Compared to the need for liver transplantation, relatively few candidates require a combined liver and intestine transplant. Of these, most liver/intestine candidates are children. Separate policies have been enacted to offer both pediatric and adult liver/intestine candidates additional allocation priority. The researchers studied the relative risk of pre-transplant mortality for adult liver/intestine patients compared to liver alone candidates, both before and since these policies were enacted. They also studied death rates by candidate height, since adult liver candidates of shorter stature may compete for organs also needed by liver-intestine candidates.
While death rates have declined since additional priority has been given adult liver-intestine candidates, their relative risk of dying without a transplant is still nearly three times higher than that of adult liver-only patients. Liver-only candidates of shorter stature have a slightly higher mortality risk, but not to the degree of liver-intestine patients. The OPTN is considering policy adjustments to address the risk of mortality for adult liver/intestine candidates.
Is There Utility in Lung Transplantation with LAS > 60?
Embargo until Sunday, May 1 – 3:27 p.m. EDT
Authors: Leah B. Edwards, Ph.D.*, Mark L. Barr, M.D., Stuart C. Sweet, M.D., Ph.D.
Since May 2005, lung transplant candidates age 12 and older have been largely prioritized by a lung allocation score (LAS). The LAS estimates both likely wait list survival and likely post-transplant survival according to certain diagnosis groups. While most lung candidates have an LAS score of 50 or lower, a few have scores of 60 or higher.
The researchers predicted waitlist survival and transplant survival for lung candidates by LAS score ranges and compared these results with actual transplant survival for recipients transplanted over a four-year period.
As the LAS score increases, predicted waitlist survival drops dramatically. Predicted post-transplant survival also decreases with increasing LAS, but not as sharply. Actual transplant survival rates were comparable for groups of LAS scores below 60, and for recipients with LAS scores of 60 or higher who were receiving a first transplant and who were less than 55 years old. While there is a survival benefit in transplanting candidates with an LAS score of 60 or higher, this benefit is lower for those who were older than 55 and/or were receiving a repeat transplant.
The Virtual Crossmatch: National Data Show Benefits of the Change to Calculated PRA (CPRA) for Sensitized Patients after One Year
Embargo until Sunday, May 1 – 4:24 p.m. EDT
Authors: Anna Y. Kucheryavaya, M.S.*, J. Michael Cecka, Ph.D., Nancy L. Reinsmoen, Ph.D.
Panel reactive antibody (PRA) assessment has long been used in kidney placement to predict how difficult it would be to find a compatible donor kidney for candidates who have been sensitized to the major targets of transplant rejection reactions. Patients likely to reject more than 20 percent of kidneys are considered “moderately sensitized”; those likely to reject 80 percent or more of kidneys are considered “broadly sensitized.”
Since October 2009, the PRA value has been replaced in OPTN policy with a calculated PRA (CPRA), which estimates the percentage of donors who would not be compatible with a candidate based upon a “virtual” crossmatch test.
All kidney offers are subject to a crossmatch test – an immunologic test of donor and recipient blood samples for potential rejection – before the transplant is performed. A “positive” crossmatch indicates a specific unacceptable immune reaction, meaning the transplant should not take place. Using modern technology, laboratories can now identify precisely those donor antigens to which the candidate has been sensitized and list them as unacceptable. Kidneys that have unacceptable antigens are not offered to candidates who would reject them because of this positive “virtual” crossmatch test.
The researchers analyzed data for adult kidney registrations in 12-month cohorts before and after implementation of CPRA policy, as well as transplant rates for two 6-month cohorts since the policy has taken effect.
Since CPRA policy has been in effect, organ offers that were declined because of a positive crossmatch test have declined by 76 percent. The transplant rates of moderately and broadly sensitized candidates have also increased, suggesting that the policy has benefitted efficiency in kidney allocation and access to transplants for sensitized candidates.
Survival Rates of Adult Recipients of Split vs. Deceased Donor Liver Transplants: An Analysis of the OPTN Database
Embargo until Sunday, May 1 – 5:30 p.m. EDT
Authors: Wida S. Cherikh, Ph.D.*, Heung Bae Kim, M.D., Chad D. Waller, M.S.*, Simon P. Horslen, M.B.,Ch.B.
In a split liver transplant, a liver from a deceased donor is divided into two segments for transplantation into two different recipients, thus increasing patient access to available organs. Often a child or young adult receives a smaller segment; the larger segment may be transplanted into an adult. The researchers compared graft and patient survival rates of adults transplanted with either split liver (where the other segment went to a child) or whole liver transplants between March 2002 and December 2008.
Multivariable analysis showed that split liver transplantation in adults was associated with a higher, but not statistically significant, risk of graft loss within five years of the transplant as compared to whole liver transplantation. Patient survival at five years was comparable between both procedures, suggesting additional use of split liver transplants from suitable donors would better serve the needs of candidates awaiting liver transplants.
CPM: A New, Composite Metric for Detecting Problems and Identifying Best Practices in Waitlist Management
Embargo until Monday, May 2 – 2:15 p.m. EDT
Authors: Darren E. Stewart, M.S.*, Jacqueline J. O’Keefe, M.B.A.*, David M. Kappus, M.A.S.*, David C. Mulligan, M.D.
For many years, transplant programs’ post-transplant survival rates have been statistically analyzed and published to assess their actual performance and compare them to statistical expectations. While very useful, these metrics do not address programs’ pre-transplant performance, such as waitlist management. Recently a composite pre-transplant metric (CPM), combining several statistical measures of waitlist management performance, has been recommended to provide additional evaluation of transplant programs.
The researchers calculated CPMs for active liver and kidney transplant programs from 2003 to 2008 and compared the results to known events. The CPM correctly noted variations that correlated with specific events affecting programs’ pre-transplant performance. The researchers recommend that the OPTN consider using the CPM along with post-transplant survival metrics for a more complete assessment of program performance.
Results of National Survey on Referral to Kidney Transplant: The Transplant Program’s Perspectives
Embargo until Tuesday, May 3 – 3:03 p.m. EDT
Authors: Wida S. Cherikh, Ph.D.*, Deanna L. Parker, M.P.A.*, Silas P. Norman, M.D., Pang-Yen Fan, M.D.
While many people with end-stage renal disease may benefit from a kidney transplant, little is known comprehensively about when and how often they are referred for transplant evaluation. The researchers sent a survey to the surgical and medical directors of all U.S. kidney transplant programs to study the timing and rate of referrals they receive.
Of the programs that responded, most track the total number of patients referred to their program and the number eventually listed for transplantation. Less than half monitor the percentage of eligible patients that were referred for transplantation, suggesting that most do not monitor the number of potential transplant candidates. The respondents report that on average, only 15 percent of patients were referred before beginning dialysis.
The researchers recommend more attention and oversight be devoted to transplant referrals to ensure patient access, including educational efforts to encourage and improve timely referral.
Is the Kidney Donor Risk Index (KDRI) a Useful Predictor of Graft Survival for Non-Renal Organs?
Embargo until Tuesday, May 3 – 4:24 p.m. EDT
Authors: Darren E. Stewart, M.S.*, Leah B. Edwards, Ph.D.*, Robert A. Metzger, M.D.
The Kidney Donor Risk Index (KDRI) was developed to help transplant professionals determine the quality of a given donor kidney offer in terms of long-term outcome once transplanted. (A derivative of this index, the Kidney Donor Profile Index, is now being encouraged as an informational resource for kidney transplant programs to use in decisions to accept individual organ offers.) The researchers applied the same statistical model to other organ types transplanted between 2000 and 2007 to see to what degree they could predict outcomes of given organ offers.
The analysis showed that the KDRI had moderate predictive power for liver, pancreas and heart donors: higher KDRI values were associated with a higher risk of graft failure, and vice versa. The KDRI did not, however, validate well as an indicator of lung donor quality; additional study would be needed to assess whether a useful predictive model could be developed for evaluating lung donors.
Invited Presentations
John Rosendale, M.S., Senior Performance Analyst in UNOS’ Research Department, will deliver two invited presentations as part of ATC panel discussions: “Measuring Yield: Improving Metrics Over Time” at 8:30 a.m. Saturday, April 30, and “Kidney Discards: New Data by Donor Risk Index” at 7:00 a.m. Sunday, May 1. Both presentations will feature summaries of recent data analyses.
The Organ Procurement and Transplantation Network (OPTN) is operated under contract with the U.S. Department of Health and Human Services, Health Resources and Services Administration, Division of Transplantation by the United Network for Organ Sharing (UNOS). The OPTN brings together medical professionals, transplant recipients and donor families to develop organ transplantation policy.
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