New Kidney and Pancreas Allocation Policy: Moving to a Circle as the First Unit of Allocation - JASN
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PERSPECTIVES www.jasn.org
New Kidney and Pancreas Allocation Policy: Moving to
a Circle as the First Unit of Allocation
Ajay Israni,1,2 Andrew Wey,2,3 Bryn Thompson,2,3 Jon Miller,2,3 Vincent Casingal,4
Martha Pavlakis,5 Silke Niederhaus,6 Rachel Forbes,7 Amber Wilk,8 Warren McKinney ,1,3
Raja Kandaswamy ,9 Peter Stock,10 and Jon Snyder ,2,3
Due to the number of contributing authors, the affiliations are listed at the end of this article.
On May 31, 2018, the US Department of Health IMPLICATIONS OF SIMULATION RESULTS
and Human Services receiv ed a critical comment
raising concerns that the existing deceased donor Using the Kidney-Pancreas Simulated Allocation
liver allocation policy may not have been in compli- Model (KPSAM),3 SRTR estimated the size of the
ance with the Organ Procurement and Transplan- allocation circle(s) was a more important determi-
tation Network (OPTN) Final Rule on deceased nant of travel distance for kidneys than the num-
donor organ allocation. The Final Rule requires ber of proximity points, with the greatest travel
that OPTN organ allocation policies “shall not be distance observed in larger circles (500 NM) and
on the basis of the candidate’s place of residence or smaller distance traveled in smaller circles (150
place of listing,” except to the extent required by NM). Figure 1A shows the distribution of organ
other components of the Final Rule (42 CFR travel distance for kidney-alone transplants.
121.8(a)(8)). To better align with the Final Rule Circle size was a more important determinant
requirements, the OPTN Kidney and Pancreas of travel distance than proximity points for pan-
Transplantation Committees explored alternative creas transplants, similar to kidney-alone trans-
policies that did not use donor service area (DSA) plants. Figure 1, B and C shows the simulated
as a unit of distribution. They also discussed the distribution of organ travel distance for kidney-
feasibility of national organ distribution. However, pancreas and pancreas-alone transplants. Proxim-
shorter cold ischemia time is associated with ity points affected the travel distance within the
improved kidney allograft outcomes.1 Cold ische- circle but not outside it, because the area outside
mia time may increase with increasing distance the circle encompasses the rest of the country.
between a candidate’s transplant center and donor On the basis of these results and feedback from
hospital. Thus, the desire to limit cold ischemia the transplant community, the OPTN Board of
time was the legal basis for including a policy pref- Directors approved new kidney and pancreas allo-
erence for candidates more local to donors creating cation systems, both of which use a single circle
local priority and to “avoid wasting organs … and with a radius of 250 miles around the donor hos-
to promote the efficient management of organ pital, with a maximum of two proximity points
placement” (42 CFR 121.8(a)(2)). Therefore, the within the circle and four proximity points out-
OPTN requested simulations from the Scientific side the circle. The four points were awarded out-
Registry of Transplant Recipients(SRTR),2 with a side the circle until the distance is $2500 NMs.
circle of 150 nautical miles (NMs) and 250 NM as Supplemental Figure 2 shows the variability in
the first unit of distribution. The 250 NM size was kidney-alone transplant rates across the OPTN
selected because it represents the distance when
organ procurement teams would consider changing
Received December 1, 2020. Accepted April 11, 2021
the mode of transportation from driving to flying.
The committee also requested simulations with a Correspondence: Ajay K. Israni, Medical Director, Scientific
Registry of Transplant Recipients, Department of Medicine,
circle size of 500 NMs, which is larger than the Nephrology Division, Hennepin Healthcare System, 701 Park
median size of an OPTN region (11 regions cover Avenue, Minneapolis, MN 55415-1829. Email: isran001@umn.
edu
the entire country) (see Supplemental Methods,
Supplemental Figure 1, Supplemental Tables 1–3). Copyright ß 2021 by the American Society of Nephrology
JASN 32: 1–5, 2021 ISSN : 1533-3450/1046-667 1PERSPECTIVES www.jasn.org
A Distribution of Organ Travel Distance, Kidney-Alone
KI
1000
Travel Distance (nm)
750
500
250
0
BL
500.500.0.8
500.500.4.8
500.150.0.8
250.250.2.4
250.250.0.8
250.150.0.8
150.150.0.8
150.150.0.20
500.500.step150
500.500.step250
Scenario
Distribution of Organ Travel Distance, Kidney-Pancreas
B
KP
1000
Travel Distance (nm)
750
500
250
0
250.250.0.8
BL
500.500.0.8
500.500.4.8
500.150.0.8
250.250.2.4
250.150.0.8
150.150.0.8
150.150.0.20
500.500.step150
500.500.step250
Scenario
Distribution of Organ Travel Distance, Pancrease-Alone
C PA
1000
Travel Distance (nm)
750
500
250
0
250.250.0.8
BL
500.500.0.8
500.500.4.8
500.150.0.8
250.250.2.4
250.150.0.8
150.150.0.8
150.150.0.20
500.500.step150
500.500.step250
Scenario
Figure 1. Distribution of organ travel distance. From top to bottom: (A) kidney-alone, (B) kidney-pancreas, and (C) pancreas-alone
transplants. The figure illustrates several models of organ allocation that were simulated with concentric circle sizes for kidney and
pancreas transplants, varying from a 500 NM circle to a 150 NM circle around the donor hospital. Various proximity point scenarios
were also modeled, ranging from eight to 20, assigned linearly outside the circle edge and tapering to zero points at the maximum
distance possible between the donor hospital and a transplant center. Various proximity point scenarios were also modeled, ranging
from zero to four, assigned linearly inside the circle, and tapering to zero points at the maximum distance possible between the
donor hospital and a transplant center within the circle. The naming convention refers to circle size for kidney-alone offers, circle size
2 JASN JASN 32: 1–5, 2021www.jasn.org PERSPECTIVES
region is reduced by this new policy. The characteristics of programs’ organ-acceptance behaviors.7 Additionally, the
the kidney, kidney-pancreas, and pancreas-alone transplant KPSAM cannot model the number of transplants because
recipients for that simulation were compared for the follow- accurate information on the kidney discard process does not
ing: (1) actual transplants in 2017; (2) ten simulations using exist (e.g., acceptance models cannot include offers for even-
existing allocation policy; and (3) ten simulations using the tually discarded kidneys). The simulations for the new policy
approved future allocation policy (Supplemental Tables 4–6) predicted 5261 waitlist deaths in a year (range 5247–5271).
The characteristics of observed transplants that occurred This range overlaps with the deaths with the existing policy,
under the existing allocation policy were similar to those of which was predicted at 5237 waitlist deaths in a year (range
candidates simulated to receive transplants in simulations of 5207–5268). The large demand for kidney allografts is one
the existing allocation policy. reason why it is unlikely number of kidney transplants are
However, in the 250 NM scenario compared with existing going to decline and waitlist deaths increase significantly.
allocation policy, kidney transplants increased for pediatric, The KPSAM cannot predict changes in the supply of kid-
female, Black, Latino, and highly sensitized calculated panel ney allografts, such as those created by the opioid epidemic,
reactive antibody (cPRA) .80%–98% candidates, and for because it only has information about donors whose kidneys
those on dialysis for $5 years. The transplants in candidates were transplanted. For example, because the opioid epi-
with cPRA .98% were unchanged. Transplants decreased demic remains ongoing, it is unlikely the numbers of
slightly for nonmetropolitan candidates and those with an deceased donors and kidney transplants will decrease with
adult estimated post-transplant survival score of 0%–20%. the new allocation policy. Because the KPSAM only uses his-
Kidney-pancreas transplants were higher for female, Black, torical data, it is best interpreted as the effect of different
non-Latino, and highly sensitized candidates (cPRA $80%). allocation systems during, for example, 2017, rather than the
Pancreas-alone transplants were lower globally under effect in the years after policy implementation, which are
broader sharing. Pancreas-alone candidates aged $35 years not yet observed.
or with cPRA $80% underwent slightly more transplants The KPSAM cannot accurately predict the number of
than those aged ,35 years or with cPRA ,80%. transplants at each transplant program because it assumes
Allocation systems attempt to balance to equity versus effi- no differences in offer acceptance across programs, which is
cacy.4 The simulations show a decline in variability in kidney not true in practice. Our modeling did not account for cost,
transplants across the OPTN region with the new policy. particularly the cost of transporting the allograft from the
There was a declinein the standard deviation across DSAs of donor hospital to the recipient’s transplant program. Given
median time on dialysis for kidney-alone transplants from the relatively longer distances in the new policy, transporta-
433 days (range, 419–446) for the existing policy versus 417 tion costs could increase. The KPSAM does not predict cold
(range, 397–438) for the new policy, in the simulations. Thus, ischemia time. Cold ischemia time is not necessarily well
allocation using 250 NM circles is likely to improve equity correlated with the distance an organ travels because the
compared with the existing system, which uses DSAs and receiving center can often expedite the crossmatch testing by
OPTN regions. The median size of a DSA in the country is 98 requesting blood sample from the donor before organ recov-
NMs, and the median size of the OPTN regions is 265 NMs. ery. This is currently done for some kidneys that come from
The proximity points are for increasing efficacy by minimiz- afar. The SRTR will monitor the effect of the new policy on
ing the distance an organ travels, and potentially reducing cold ischemia time.
cold ischemia time inside and outside of the circle. The new policy does create borders; therefore, OPTN has
The simulation models predicted an increase in kidney- already started working toward a borderless allocation
pancreas transplants (existing policy, 815; new policy, 1056) systems.8
and a corresponding decrease in kidney-alone transplants
(existing policy, 13,080; new policy, 12,830) and pancreas-
alone transplants (existing policy, 158; new policy, 94). SUPPLEMENTAL CONCISE METHODS FOR THE SRTR
Importantly, the increase in kidney-pancreas transplants SIMULATIONS
largely explained the decrease in kidney-alone transplant.
Annually, the number of kidney-pancreas transplants The OPTN committees wanted to provide candidates listed
is increasing, whereas pancreas-alone transplants are closer to the donor hospital priority to achieve best use of
decreasing.5,6 organs, while mitigating the effects of further travel logistics
The simulations have several limitations. Most important, and outcomes (Supplemental Table 1, Supplemental Figure
the KPSAM cannot account for changes in transplant 1). The new policy retained features on the existing kidney
for kidney-pancreas and pancreas alone offers, maximum proximity points within the circle, and maximum proximity points outside
the circle. The last two models on the extreme right have a single allocation circle, but all candidates within 150 or 250 NM, respec-
tively, receive the maximum four proximity points. BL, baseline or existing policy; 250.250.2.4, new policy.
JASN 32: 1–5, 2021 Kidney Allocation Policy 3PERSPECTIVES www.jasn.org
policy, including risk stratification of deceased kidney Instead, the average and range of results for the ten itera-
donors using the Kidney Donor Profile Index and candi- tions are described for the existing and proposed policies.
dates by estimated post-transplant survival, among others
(Supplemental Table 2). As in the existing system, the same
allocation points will be used to rank candidates in each DISCLOSURES
classification listed in Supplemental Table 3, but with the
inclusion of proximity points (Supplemental Table 1).7 The A.K. Israni reports receiving grant fundingfrom CSL Behring and has been
new policy also retained features of the existing pancreas, a member of an Advisory Board to CSL Behring, outside of this work; and
reports receiving research funding from Gilead outside of this work. A. Wey
kidney-pancreas, and islet policy that risk stratifies deceased
reports patents and inventions with University of Minnesota, clinical severity
donor pancreata from deceased donors aged #50 years with questionnaire for Sanfilippo Syndrome; and reports other interests/relation-
a body mass index #30 kg/m2.9 ships as a biostatistician on the federal contract for the SRTR. B. Thompson
reports receiving research funding from Atara Biotherapeutics. M. Pavlakis
reports receiving research funding as principal investigator for the APOL1
Long-Term Kidney Transplantation Outcomes Network study and PI on a
STUDY POPULATION FOR SIMULATIONS
trial for the Trugraf Genomics study TruGraft Long-term Clinical Outcomes
Study; and reports other interests/relationships with EBSCO Industries Inc. as
The SRTR data used included all deceased kidney donors, wait- content writer, and Transplant Solutions as a consultant. J. Snyder reports
list candidates, and transplant recipients in the United States receiving research funding from Astellas, Atara Biotherapeutics, CSL Behring,
and has been described previously.2 This included all trans- and Novartis; reports receiving honoraria from CareDx; reports being a scien-
plant candidates on the kidney, kidney-pancreas, and pancreas tific advisor or member as Board Member of the Organ Donation and Trans-
plantation Alliance, Board Member of Donate Life America, LifeSource Clini-
waiting lists from January 1, 2017 to December 31, 2017, and cal Policy Board, Transplantation as Associate Editor, American Journal of
any offers for a pancreas or kidney for an eventually accepted Transplantation as Statistical Editor; and reports other interests/relationships
organ from donors recovered during this period. as Director of SRTR. P. Stock reports being a scientific advisor or member of
Encellin. R. Kandaswamy reports consultancy agreements with CareDX,
Natera, TRACT Therapeutics (pending), and Vertex Pharmaceuticals; reports
being scientific advisor or member with LifeSource as a Member of Clinical
MODELING APPROACH
Policy Board, Senior Staff of Pancreas Transplantation; and reports speakers
bureau with Natera and SRTR. S. Niederhaus reports receiving honoraria from
This study used the KPSAM, which is routinely used by the American Diabetes Association (ADA) as a speaker in 2019 on pancreas
OPTN committees to assess potential policy proposals.3 The transplantation and honorarium donated to the ADA; reports being a scientific
KPSAM simulates both the arrival of donated organs and advisor or member of the National Kidney Foundation of Maryland/Delaware
new candidates on the waiting list over a 1-year period using Board of Directors Member, OPTN Pancreas Committee Chair through July
1, 2020; and reports other interests/relationships with American Society of
actual SRTR data. With each new organ arrival, it mimics Transplantation, American Society of Transplant Surgeons, International Pan-
the actual organ allocation by generating a match run creas & Islet Transplant Association, National Kidney Foundation of Mary-
according to the programmed allocation policy. Specifically, land/Delaware as above, and other academic societies.
it checks compatibility of organs with candidates on the
waiting list at the time an organ becomes available, creates
ordered lists of compatible candidates (candidates with FUNDING
more priority points have priority for receiving the organs
over candidates with fewer points in each ordered list), and This work was supported by the US Department of Health and Human
Services, Health Resources and Services Administration, Healthcare
simulates candidate acceptance or refusal of organ offers Systems Bureau, Division of Transplantation, the Hennepin Healthcare
using a logistic regression model. This logistic regression Research Institute, contractor for the SRTR, as a deliverable under contract
uses donor factors only, and is on the basis of actual organ HHSH75R60220C00011 and United Network for Organ Sharing, contractor
for the OPTN, under contract 250-2019-00001C.
acceptance behavior in 2017. The logistic regression model
did not include candidate factors because the pool of candi- ACKNOWLEDGMENTS
dates in a concentric circle–based policy would look differ-
ent than in the existing allocation policy. On the basis of As a US government-sponsored work, there are no restrictions on the use
these inputs, KPSAM calculates the number of transplants of this study. The views expressed herein are those of the authors and not
and organs discarded. This process is repeated ten times in necessarily those of the OPTN and US government. The authors thank
SRTR colleague Ms. Mary Van Beusekom ELS, for manuscript editing.
KPSAM for both the existing allocation policy and for each
proposed allocation policy, each time randomly permuting
the order of donor arrivals and generating new random
SUPPLEMENTAL MATERIAL
numbers to determine organ offer acceptance. Statistical
tests of comparisons are not useful because randomness of
This article contains the following supplemental material online at http://jasn.
the simulation modeling is the only source of variability. asnjournals.org/lookup/suppl/doi:10.1681/ASN.2020121679/DCSupplemental.
Thus, all comparisons would have “statistically significant” Supplemental Figure 1. Scenario modeled for new kidney and pancreas
differences if the simulation is repeated enough times. allocation policy.
4 JASN JASN 32: 1–5, 2021www.jasn.org PERSPECTIVES Supplemental Figure 2. Maps of transplant rate by OPTN region for kid- REFERENCES ney transplants alone. Supplemental Table 1. Overview of scenarios modeled for new kidney 1. Wong G, Teixeira-Pinto A, Chapman JR, Craig JC, Pleass H, and pancreas allocation policy, along with existing policy. McDonald S, et al.: The impact of total ischemic time, donor age Supplemental Table 2. The new policy retained features of the existing and the pathway of donor death on graft outcomes after kidney policy, including risk-stratified deceased donor kidney using kidney deceased donor kidney transplantation. Transplantation 101: donor profile index and candidates by estimated post-transplant survival. 1152–1158, 2017 Inner circle refers to candidates within the concentric circle around the 2. Leppke S, Leighton T, Zaun D, Chen SC, Skeans M, Israni AK, et al.: donor hospital. Scientific Registry of Transplant Recipients: Collecting, analyzing, and Supplemental Table 3. (A) Priority point system for new kidney allo- reporting data on transplantation in the United States. Transplant Rev cation identical to existing policy. Proximity points, as described in (Orlando) 27: 50–56, 2013 Table 1, were added to these priority points. (B) Priority points 3. Scientific Registry of Transplan t Recipients. Kidney-Pancreas Simu- awarded based on the calculated panel-reactive antibodies identical to lated Allocation Model. 2015. Available at: https://www.srtr.org/ existing policy. requesting-srtr-data/simulated-allocation-models/. Accessed June 2, Supplemental Table 4. Characteristics of actual kidney recipients in 2017 2021 and those in simulations of existing policy and proposed policy, percentage 4. Caplan A: Bioethics of organ transplantation. Cold Spring Harb Per- (n). The new kidney and pancreas allocation policies, both of which use a spect Med 4: a015685, 2014 concentric single circle with a radius of 250 nautical miles around the donor 5. Kasiske BL, London W, Ellison MD: Race and socioeconomic factors hospital and a maximum of 2 proximity points within the circle 4 proximity influencing early placement on the kidney transplant waiting list. J points outside the circle. Am Soc Nephrol 9: 2142–2147, 1998 Supplemental Table 5. Characteristics of actual kidney-pancreas recipi- 6. Kandaswamy R, Stock PG, Gustafson SK, Skeans MA, Urban R, Fox ents in 2017 and of recipients in simulations of existing policy and the A, et al.: OPTN/SRTR 2018 Annual Data Report: Pancreas. Am J new policy, percentage (n). The new kidney and pancreas allocation Transplant 20[Suppl s1]: 131–192, 2020 policies, both of which uses a concentric single circle with a radius of 7. Israni AK, Salkowski N, Gustafson S, Snyder JJ, Friedewald JJ, For- 250 nautical miles around the donor hospital and a maximum of 2 mica RN, et al.: New national allocation policy for deceased donor proximity points within the circle and 4 proximity points outside the kidneys in the United States and possible effect on patient outcomes. circle. J Am Soc Nephrol 25: 1842–1848, 2014 Supplemental Table 6. Characteristics of actual pancreas recipients in 8. Snyder JJ, Salkowski N, Wey A, Pyke J, Israni AK, Kasiske BL: Organ 2017 and of recipients in simulations of existing policy and the new policy, distribution without geographic boundaries: A possible framework for percentage (n). The new kidney and pancreas allocation policies, both of organ allocation. Am J Transplant 18: 2635–2640, 2018 which uses a concentric single circle with a radius of 250 nautical miles 9. Smith JM, Biggins SW, Haselby DG, Kim WR, Wedd J, Lamb K, et around the donor hospital and a maximum of 2 proximity points within al.: Kidney, pancreas and liver allocation and distribution in the the circle and 4 proximity points outside the circle. United States. Am J Transplant 12: 3191–3212, 2012 AFFILIATIONS 1 Department of Medicine, Hennepin Healthcare, University of Minnesota, Minneapolis, Minnesota 2 Scientific Registry of Transplant Recipients, Minneapolis, Minnesota 3 Hennepin Healthcare Research Institute, Minneapolis, Minnesota 4 Department of Surgery, Carolinas Healthcare, North Carolina 5 Department of Medicine, Beth Israel Deaconess, Harvard, Boston, Massachusetts 6 Department of Surgery, University of Maryland, Baltimore, Maryland 7 Department of Surgery, Vanderbilt University, Nashville, Tennessee 8 United Network for Organ Sharing, Richmond, Virginia 9 Department of Surgery, University of Minnesota, Minneapolis, Minnesota 10 Department of Surgery, University of California at San Francisco, San Francisco, California JASN 32: 1–5, 2021 Kidney Allocation Policy 5
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