What will change?
Instead of an algorithm based on levels of priority, the new proposed algorithm is based on a continuous points score. The advantage of this approach is that it considers the complete picture of a person when determining their rank in the offer list, not simply whether they meet the criteria for a single priority category.
How will patients benefit?
The new algorithm is specifically designed to offer better-matched kidneys to waitlisted patients. Simulations of the new algorithm indicate that patients will be more likely to be offered a kidney that is a good immunological match for them. Offers are also predicted to be more closely matched in terms of expected longevity of kidney and recipient.
Differences in waiting times between ethnic groups are also predicted to be reduced, resulting in a fairer system.
About the New Algorithm
Kidney Allocation in Australia
Australians who are on the waiting list for a deceased donor kidney transplant are offered kidneys according to an algorithm that is run by OrganMatch each time that a suitable deceased donor is referred. The kidney allocation algorithm is a set of rules that determine which kidneys will be offered to which waitlisted patients, and in what order.
Although we commonly refer to the “waiting list”, a more accurate description would be a “waiting pool”. When a deceased donor becomes available, the allocation algorithm creates a ranked list of potential compatible recipients from the pool of eligible recipients. Whether a potential recipient ranks high or low on this list will depend on recipient characteristics such as length of waiting time, but it will also depend on how well-matched they are with that specific donor. The order of the list is therefore slightly different for every donor, with better-matched recipients closer to the top. The rules which govern the allocation of deceased donor kidneys are separate from the rules that determine who is eligible to go on the kidney transplant waiting list (i.e. eligibility criteria). Eligibility criteria consider factors such as comorbid conditions and the current health status of the patient, their risk of complications and capacity to benefit from a transplant, and their ability to adhere to complex medical treatment post-transplant. Once a person is determined to meet the eligibility criteria and is added to the deceased donor kidney transplant waiting list, the cause of their kidney disease, their comorbid conditions, and their health-related behaviours do not influence kidney allocation.
Kidney allocation in Australia is based on the following principles:
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All eligible waitlisted persons, regardless of ethnicity, gender, or state/territory of residence, have an equal right to transplantation
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People who have been on dialysis for longer should have higher priority
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Priority should be given to people for whom it is particularly difficult to find a compatible kidney, to give them a more equal chance at getting transplanted
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The allocation system should seek to maximise the life years saved from available donor organs
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Children and young people should receive priority over older adults for well-matched kidneys.
The Current System
How does it work?
The current Australian deceased donor kidney allocation algorithm includes a “National Allocation Algorithm” and a “State Allocation Algorithm”. Kidneys are offered first via the National Algorithm, then via the State Algorithm.
Full technical details of the current Australian kidney allocation algorithm are found here.
NATIONAL ALLOCATION ALGORITHM
Kidneys are first offered by the National Allocation Algorithm to high priority recipients in the following order:
National Priority Level 1: Very highly sensitised individuals (PRA >=95%)
National Urgent Status: National urgent Listings (exceptional circumstances only)
National Priority Level 2: Good immunological matches for young recipients
STATE ALLOCATION ALGORITHM
If not allocated at the National Level, kidneys are offered to recipients in the same state as the donor in the following order:
State Urgent Status: Persons deemed as urgent by the State Advisory Committee
Priority Level 1: Good immunological matches
Priority Level 2: Persons who have been waiting the longest
The National Algorithm is designed to give first access to kidneys, regardless of where they were donated, to patients who meet certain priority criteria. About one-third of kidneys are currently allocated via the National Algorithm. The rest are allocated according to the State Algorithm, which allocates kidneys to recipients in the same state as the donor.
Bonus points for paediatric patients are given as part of both the National and State Allocation Algorithms. These bonus points mean that, all else being equal, a recipient under 18 years will get priority over an adult recipient.
In addition, the State Algorithm gives extra priority where the expected life span of the kidney is well-matched to the prognosis of the recipient. This is called “prognosis matching” and is achieved by matching the Kidney Donor Profile Index (KDPI) with the Expected Post-Transplant Survival (EPTS) score for the recipient.
Lastly, waiting time is used to differentiate between potential recipients who are otherwise similar. That is, all else being equal, the person who has been waiting longest has priority.
Why does it need to change?
The current system is largely effective at delivering fair allocation outcomes that respect waiting times while also addressing the needs of very highly sensitised individuals. However, it does have some limitations and areas where it could be further optimised. The key limitations of the current system are as follows:
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It is based on a series of hierarchical levels of priority, defined by hard cut-offs. These hard cut-offs at the transition from one level of priority to the next can produce allocation outcomes that seem arbitrary or even unfair.
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The system could do more to maximise the number of life-years saved from kidney transplantation (system utility). The current criteria for matching the expected lifespan of the kidney with the expected lifespan of the recipient are very broad and still permit very wide differences in prognosis.
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The current rules around immunological matching mainly benefit those individuals who are easy to match; persons with uncommon HLA profiles are at a disadvantage.
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Individuals from minority ethnic groups (including Indigenous Australians) have longer average waiting times, related in part to the greater difficulty of finding a good immunological match.
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The paediatric bonus ends at age 18, causing anxiety for waitlisted young people as their 18th birthday approaches.
The design of a new allocation system presents an opportunity to address these limitations. Any new system, however, will still be constrained by the number of deceased donor kidneys available for transplantation in Australia. Although we may be able to make changes that bring differences in waiting times between different population groups to within acceptable limits, a new allocation system cannot reduce waiting times overall, as to do this would require an increase in the number of available donors.
Creating a New Algorithm
How was it developed?
A Working Group was formed by the Renal Transplant Advisory Committee of the Transplantation Society of Australia and New Zealand in 2023, with the task of developing a new algorithm for the allocation of deceased donor kidneys in Australia. This Working Group included representatives from all Australian transplant regions (QLD, NSW/ACT, VIC/TAS, SA/NT, WA) and met monthly for approximately 18 months. A Biostatistics Focus Group, formed from the wider Working Group, developed and ran simulations and tested various proposals. The development of the new algorithm involved 4 main phases: 1.Identification of the limitations of the current system and the objectives of the redesign 2.Identification of the ideal future state and options for how to get there 3.Running of simulations and sensitivity analyses for different options, followed by evaluation of outcomes 4.Consultation with stakeholders. The consultation phase of this project involved presentations to and discussions with the wider nephrology community, transplant clinicians, donor coordinators, transplant nurses, transplant recipients and waitlisted patients.
Algorithm development process
Identify objectives
Identify design options
Simulate and test
Consultation and public comment
Board approval
This proposal is now open for public comment, prior to being submitted to the TSANZ Board for approval. Once the TSANZ Board has approved the proposal, it will be submitted to OrganMatch with a recommendation to implement.
Goals and Objectives of the New Algorithm
Equity
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Minimise differences in waiting times by gender, ethnicity, Indigenous status, location of residence
Waiting Time
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All other factors being equal, the person who has been waiting the longest has priority (queuing equity)
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The differences between population groups in their waiting times should be within acceptable limits
Sensitised Patients
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Minimise the disadvantage caused by antibodies/sensitisation status
Immunological matching
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Reduce future sensitisation for those expected to need repeat transplantation
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Reduce the risk of antibody mediated rejection and extend graft survival
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Avoid creating inequities for specific groups/ethnicities
Maximising life years saved from transplantation
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Maximise longevity of the highest quality kidneys by allocating to recipients who are expected to benefit the most from them
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Faster access to kidneys with a shorter expected lifespan for those who might benefit from them
Paediatric patients and young people
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Reduce the risk of sensitisation against future transplants
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Minimise time on dialysis for paediatric patients
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Match younger recipients with kidneys with a long expected lifespan
The Proposed New Algorithm
How is it different to the current algorithm?
Instead of a algorithm based on levels of priority and hard cut-offs, the new proposed system is based on a continuous points score. The advantage of this approach is that it considers the complete picture of a person when determining their rank in the offer list, not simply whether they meet the criteria for a single priority category. It will change the way that patients are ranked in allocation by considering multiple patient factors simultaneously.
Internationally, the UK and France have already incorporated continuous points scores into their kidney allocation systems. The United States are also in the process of introducing a continuous points score.
How would the new algorithm work?
The Figure below illustrates how a continuous points-based approach to allocation would work. Waitlisted individuals receive points for various attributes (represented by the different coloured bars, the length of the bar indicates the number of points given). The points are added together to give a final allocation score.
Each attribute has a specific weight, meaning some attributes will have more effect than others on the total allocation score, yet no one attribute will decide an organ match.
A individuals’ total score will determine their rank order in the offer list.In this example, Patient C receives the most points and would get the first offer.
Each colour in the chart above corresponds to a different attribute of the recipient or the match. The length of the bar shows the number of points given to the potential recipient and is a composite of the points awarded for each attribute.
Under the proposed new Australian kidney allocation algorithm, all waitlisted patients will receive a continuous allocation score based on the sum of points awarded for the following attributes:
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Waiting time
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The quality of the HLA match (is this a good immunological match for this person?)
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PRA value (more sensitised = higher points)
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Prognosis matching (difference between EPTS and KDPI)
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Home state bonus (1 bonus point for recipients in the same region as the donor)
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Urgent or other priority status (applies in limited specific situations).
To view the technical specifications for the calculation the continuous allocation score, click below
How will patients benefit?
A computer simulation of the proposed new allocation system was constructed to examine predicted outcomes, including waiting times, the quality of the immunological matching, and the extent of prognosis matching. Predicted outcomes for the new system were then compared to the observed outcomes for the current system.
The key predicted changes compared to the current system are:
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Better prognosis matching overall (learn more about prognosis matching here)
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Better immunological matching of donors to recipients, especially for younger people and for ethnic minority groups
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Less disparity in waiting time by ethnicity (i.e. waiting times are more equal across ethnic groups)
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Slightly reduced waiting times for highly sensitised patients
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Lower waiting times for 18-34 year-olds (average of approximately 6 months shorter waiting time), but slightly higher waiting times for 50-64 year olds (average of approximately 2 months longer waiting time)
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Slightly reduced waiting times for 65+ age group and closer prognosis matching.
For more simulated outcomes of the new system, click "Simulated Outcomes" below.
How will I be affected?
The new system would potentially affect which kidneys are offered to you and, in some cases, how long you will need to wait.
The new system is specifically designed to offer better-matched kidneys to waitlisted patients, both in terms of their expected longevity and the quality of the immunological match. Our simulations indicate that you will be more likely to be offered a kidney that is a good immunological match for you personally. Offers are also predicted to be more closely matched in terms of expected longevity.
The following hypothetical cases describe how the new system would affect patients at the individual level.
"BEN"
Age: 21
Blood group: A
PRA: 0%
Ethnicity: Caucasian
Modelling indicates remaining waiting time would be slightly reduced under the new system, due to greater emphasis on good matches for young people. The quality of HLA-matching of offers would be improved.
"SOPHIE"
Age: 35
Blood group: B
PRA: 85%
Ethnicity: Caucasian
Modelling indicates remaining waiting time would be significantly reduced under the new system, due to greater emphasis on good matches for young people and changes to how sensitised individuals are prioritised. The quality of HLA-matching of offers would be improved.
"MARGARET"
Age: 54
Blood group: A
PRA: 20%
Ethnicity: Caucasian
Modelling indicates remaining waiting time would be slightly increased under the new system. This is because of additional priority going to young people.
"JOHN"
Age: 42
Blood group: A
PRA: 0%
Ethnicity: Aboriginal
Modelling indicates remaining waiting time would be reduced under the new system. Changes to how HLA-matching is prioritised increases transplant opportunities for ethnic minorities (including Aboriginal and Torres Strait Islander patients) and difficult to match patients.
"AN"
Age: 52
Blood group: O
PRA: 0%
Ethnicity: Asian
Modelling indicates remaining waiting time would be slightly reduced under the new system, due to changes to blood group compatible rules that reduce inequities for blood group O patients.
"CLAIRE"
Age: 56
Blood group: A
PRA: 98%
Ethnicity: Caucasian
Modelling indicates remaining waiting time would be reduced under the new system, due to changes to how sensitised individuals are prioritised. The quality of HLA-matching of offers would be improved.
Multiorgan Transplants
Simultaneous pancreas-kidney (SPK) transplantation
The majority of solid organ pancreas transplants in Australian are undertaken as simultaneous pancreas and kidney (SPK) transplants in recipients with both type 1 diabetes and kidney failure. There were 40 SPK transplants performed in Australia from August 2022 to July 2023.
Under the current Australian allocation system, when a pancreas is donated for SPK transplantation, one of the donor kidneys is also allocated to the same recipient. The second kidney is then made available to be allocated to a kidney-only recipient according to the standard kidney allocation algorithm. However, if there are two potential kidney-only recipients who qualify for Level 1 or Level 2 National priority (due to being highly sensitised or a very good immunological match) then the allocation to the SPK patient will not occur (i.e. will be vetoed) and the kidneys will be allocated to the two kidney-only patients instead.
Under the proposed new allocation system, when a suitable pancreas is donated for SPK transplantation, one of the kidneys will also be allocated with the pancreas unless there are two potential kidney-only recipients with allocation scores of 15 points or higher.It is predicted that this new rule would lead to a small reduction in waiting time for SPK patients. SPK patients can also be dual-listed on the kidney-only waiting list. If they receive an offer from the kidney list and the pancreas is suitable and available, an SPK transplant can proceed. This is particularly relevant to SPK patients who are also highly sensitised and need the large points bonus that is given to highly sensitised patients in order to increase their chance of receiving any transplant.
Other multi-organ transplantation
Under the current kidney allocation system, recipients who need a combined kidney-liver, kidney-heart, kidney-lung or other multi-visceral transplant have priority over all kidney-only and SPK transplants. When a suitable liver, heart or lung arises, the kidney is offered along with the other organ and is not offered to the kidney-only list.
Under the proposed new allocation system, kidney-liver, kidney-heart, kidney-lung, and other multi-visceral transplants will continue to have priority over kidney-only and SPK transplants.
What next?
We are now inviting feedback from the wider community on this proposed new kidney allocation system. The public comment phase will close on May 15, 2025.
Feedback received during the public comment phase will be reviewed and discussed by the Kidney Allocation Working Group and responded to as appropriate. A written response to the comments received by the wider community will be posted on the TSANZ website.
Following the completion of the public comment phase, the specifications of the new kidney allocation algorithm, a report detailing its development and underlying rationale, and a summary of feedback received through the consultation phase will be submitted to the Renal Transplant Advisory Committee and then to the TSANZ Board for approval. Once approved, the algorithm specifications will be submitted by TSANZ to the Organ and Tissue Authority and the OrganMatch Governance Committee with a recommendation to implement.
Monitoring the New Algorithm
Following implementation, the outcomes of the new algorithm would be closely monitored (with the oversight of the Renal Transplant Advisory Committee) for any unintended consequences of the change. A detailed monitoring plan has been prepared as part of this project, based around carefully chosen metrics.
If unintended or unexpected outcomes of the system become apparent through monitoring, steps will be taken to make revisions the new algorithm, to bring outcomes back in line with system objectives.
Submit your feedback
We are now inviting feedback from the wider community on this proposed new kidney allocation system. If you have feedback that you wish to share, you can either email sarah@tsanz.com.au or use our online form