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Organ allocation must be fair and just.
Public willingness to donate organs depends on a transparent and fair allocation system.
Deceased donation is not directed to a specific individual,
it is a gift to society.
And what we do with a gift is a reflection of our society.
We must not discriminate between patients and we must ensure that
everyone has a fair chance of receiving an organ, should they need it.
Unfortunately, there are not
enough organs available to transplant everybody on the waiting list.
And the reality is that people die every day while waiting.
Allocation policies have life and death consequences for patients.
So, how do we ensure the system is fair for everyone?
Firstly, you do it by ensuring that allocation is transparent and accountable.
There must be a set of rules to which everyone adheres
and these must be freely available for scrutiny.
Ethically, the allocation process comes down to
two factors that need to be balanced; justice and utility.
Justice requires it to be a fair consideration of
the candidates circumstances and medical needs.
The most commonly used markers for justice are
time on the waiting list and medical urgency.
Utility requires that we maximize the amount of benefit
gained from each organ transplanted across the whole population.
The most commonly used markers of benefit are
the number of people and the number of life he has gained from the donor.
These two factors are not easy to balance.
Take for example two patients on the kidney waiting list.
If they differ solely on the basis of age one is
14 years old and the other is 60 years old, who should get the kidney?
Let's say the 14 year old is a type
one diabetic adolescents and diabetics do worse than your average patient.
That say the 60 year old is highly
sensitized and unlikely to ever have a negative cross match.
What if a 14 year old has been waiting for three years longer or
the kidney donor is a very old donor with hypertension.
Bear in mind I have given you an example with just two patients.
The waiting list for a kidney in the United States alone is almost 100,000 people.
So,what do we actually do when it comes to allocation.
This seems a challenging problem.
Well first up, comes some logistical considerations.
The cold ischaemic time influences transplant outcomes.
So, traveling across the length of a country or the world with an organ
and extending the cold ischaemic time has consequences.
Organs are therefore allocated within defined geographical areas.
For some organs, size matching impacts on function.
You physically can't put the heart of
a hundred kilogram adult into a three year old child and vice versa.
So there are accepted size discrepancies between donor and
recipient for heart, liver and lungs.
Kidneys are transplanted extra anatomically,
not in the place of the native kidneys and size is not an issue.
Livers of good quality can be cut down to the required size,
but they can be made bigger.
Allocation is also done within blood groups,
transplantation across blood groups although possible, is more risky.
By allocating within blood groups,
we also ensure that blood group O,
who are universal donors are not discriminated against.
All blood groups A, B,
AB and O can receive from blood group O,
but blood group O,
can only ever receive from another blood group O.
Next, you need to have a negative cross match.
This requires testing the blood of
the donor against the blood of the potential recipient.
All patients on the waiting list have samples of their blood sent
regularly to the tissue typing laboratory.
If the test is positive,
this means that the organ would be immediately rejected by the recipient.
Only patients with a negative cross match
can receive an organ from that particular donor.
The likelihood of a negative cross match can be predicted
beforehand from a test called the PRA, panel reactive antibody.
If you have a 99% PRA,
that means that only one out of 100 donors is likely to have a negative cross with you.
Allocation scores can give way to the PRA,
so that opportunities to transplant highly sensitized patients are not missed.
All donor organs are not equal,
all are needed but some will work better than others.
In our South African system,
we allocate kidneys from all the donors to all the recipients.
Our age cutoff is 50 and from paediatric donors to paediatric recipients.
These are the basic principles of allocation,
but each organ uses a specific algorithm to allocate.
For kidney allocation, systems use primarily a composite measure
of time on the waiting list and closeness of HLA matching.
These correlate with justice,
first come first served and utility,
the better the match, the longer the kidney will last.
HLA matching is of importance in kidney allocation because kidneys are
more immunogenic and therefore more likely to be rejected than other organs.
The closer you are HLA match to your donor,
the longer the kidney will last.
Everyone's ideal donor would be an identical twin.
The further removed you are from the donor,
the stronger the immunosuppression you will need to
take and the higher the chance of rejection in the long term.
In the South African system,
with our diverse population,
we don't allocate based on HLA matching,
unless it's a perfect match.
This helps to ensure that there is no racial discrimination in allocation of donors,
an important consideration for our Rainbow Nation.
Other countries rely to some degree on HLA matching.
The utilitarian argument of making transplanted organs last the maximum length of time,
trumping the justice argument.
In the United Kingdom,
there has been a large drive in deceased donor education programs to target
ethnic minorities because these groups wait on average
a year longer than the general population for a kidney transplant.
The reasons for this is multi-factorial,
they have higher rates of hypertension and diabetes and kidney disease,
but they also have a much lower decease donation concentric.
For organs other than the kidney,
time on the waiting list is not a good way to differentiate patients.
For other organs there are no long term treatment options like dialysis.
For organs such as heart, liver and lungs,
medical agency is more heavily weighted,
the sickest patient is transplanted first.
If there is a tie, then it comes down to other factors such as,
time on the waiting list or anticipated cold ischaemic time.
Allocation of hearts, classify patients to status one or status two.
Status one means the patient is on some form of
continuous mechanical support or
a continuous infusion of medication to support the heart.
Allocation of adult livers is based on the MELD score comprised of bilirubin,
creatinine and INR as this correlates with expected mortality.
Additional points are given over time to patients with liver malignancies,
who can be cured with a transplant as
these patients often have preserved liver and renal function.
Lungs use the Lung Allocation Score.
This is comprised of a waiting list urgency measure,
that is the number of expected days a candidate will live without a transplant and
a post transplant survival measure which is
the expected number of days a candidate will live if they do receive a transplant.
As you can see, organ allocation is quite complicated, not easy,
but as long as the rules are agreed upon and are there for everyone to see,
we can have a system that can be held accountable.
Each country has their own organ allocation system,
United States is the largest transplant program in
the world and organ allocation is governed by UNOS,
the United Network of Organ Sharing which periodically reviews and refines this system.
In South Africa, we have a much smaller transplant program.
Organs are allocated on a national basis for urgent heart,
liver and lung requests,
but if there is no urgent national call then organs are allocated locally.
Kidneys are always allocated to recipients from the province of the donor.
And because we have no formal remuneration system for the donor hospital,
one kidney gets allocated to the top of
the donor hospital's waiting list or the other gets allocated to
the top patient on the provincial waiting list which
is a combined public and private list.
To recap, great effort is taken to ensure organ allocation is fair and accountable.
These are life and death decisions for patients because we
are not able to transplant an organ to everyone who needs one.
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David ThomsonDr
