NHS BLOOD AND TRANSPLANT
I NEED A KIDNEY TRANSPLANT BUT MY LIVING DONOR IS NOT COMPATIBLE
WITH ME. WHAT ARE MY CHANCES IN THE PAIRED DONATION SCHEME?
INTRODUCTION
People who need a kidney transplant may receive a kidney from a living or deceased
donor. Some people may have a family member or close friend who wishes to be a
donor but the kidney is not suitable for the intended recipient because the blood
groups or HLA types (tissue type) are not compatible.
The Paired Donation scheme is part of the National Living Donor Kidney Sharing
Schemes (NLDKSS) and was originally set up to allow incompatible donor and
recipient pairs the opportunity to ‘swap’ kidneys with other pairs. Patients may now
also choose to enter the scheme if they have a compatible donor but wish to see if it
is possible to be matched with another donor who is a closer age or HLA match.
Because the system depends on the availability of other suitable pairs in the scheme
at the same time, it is difficult for patients and transplant teams to know how likely it
is that they will get a transplant through the scheme.
This tool was developed to give patients who are thinking about entering the scheme
an estimate of how long they can expect to wait for a transplant. It is tailored to the
characteristics of both the donor and the recipient and also gives an estimate of the
likely waiting time for a deceased donor kidney transplant. The tool is designed to be
used with the advice and help from your Transplant Unit Coordinator, Nurse or
Doctor and we advise that you discuss it with them and use it together to help you
decide what suits you best. It can be found at
http://www.odt.nhs.uk/transplantation/guidance-policies/tools/.
.
More technical details are given in the end section ‘Further information’.
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HOW TO USE THE TOOL
Once opened, the screen should look this
Opening screen shot
On the left hand side of the screen you will see a number of drop-down boxes. A
selection must be made in each box before the results will be shown.
You may not know all the details required which is why we strongly suggest that you
use this with your Transplant Unit Coordinator, Nurse or Doctor who can give you the
necessary information as well as help you decide what is the best option for you.
INTERPRETING THE RESULTS
The tool shows the estimated chance of a transplant for 3 different scenarios: a
transplant from a deceased donor, a transplant through the paired donation scheme
and a living donor transplant that is ABO (blood group) or HLA incompatible.
The transplant survival figure gives an estimate of the likelihood of the graft still
working at 6 months, 1 and 3 years after the operation.
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An example
An example of how the results are presented is shown below. We have entered the
details of the recipient and these are shown in the box in the upper left corner of the
screen.
Example results
Estimated Chance of Transplant:
The chances of a transplant are shown as a percentage. So, in the Table of the
estimated Chance of a Transplant, we would estimate that between 11 and 20 of 100
people with these characteristics of the patient would receive a transplant from a
deceased donor within one year of listing. For 100 donor-recipient pairs with the
given characteristics, between 61 and 70 would be transplanted within a year through
the paired donation scheme.
Figures are also given for 6 months and 3 years.
In this example we also see that the indication of ‘Low Titre’ in the ABOi TX (blood
group incompatible transplant) variable means that a blood group incompatible
transplant is likely to be possible. Waiting times are not given in this case as the time
to transplant involves the (short) work up time to transplant only.
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Transplant Survival Rates
Again, results are given as a percentage so a figure of 91% means that in 91 cases
out of 100 people with these recipient characteristics who have received a deceased
donor kidney, will have a graft that is working well one year after the transplant.
The table also shows that the number of working kidney transplants from a living
donor transplant is about 96% and for an ABO incompatible transplant 92%. In this
example, no data are given for HLA incompatible transplant as that information is not
relevant for this pair.
NHS Blood and Transplant
2015
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FURTHER INFORMATION
The Incompatible Pairs Living Donor Kidney Application was developed by the
Department of Statistics and Clinical Studies in Microsoft (MS) Excel Professional
Edition (2010). To use the software MS Excel 2003 or later versions will be required
although there may be other conversion software available capable of running this
program.
Macros and security settings: On opening the software in MS Excel, and
depending on your security settings, you may be prompted to “Enable Macros” or you
may be presented with a warning message that alerts you to the fact that the
software has embedded macros. If you do not choose to enable or accept macros
then it will not be possible to use this software. If security settings are set at ‘High’ the
software can still be used but you may not be able to make use of the ‘Reset’ button
embedded within the software.
DEFINITION OF INFORMATION REQUIRED
Recipient Blood Group: O, A, B or AB.
Calculated Reaction Frequency: Defined as the proportion of 10000 blood group
compatible UK donors against which the recipient has HLA specific antibodies.
Standardised calculated reaction frequency (%), defined in 3 groups: 0-84, 85-94 and
95-100.
Donor Blood Group: O, A, B or AB.
ABOi Transplant with willing Donor: The clinician should decide whether, based
on ABO titre levels, the pair could proceed with an ABO incompatible transplant in
line with the practices at that centre. Selecting ‘Low Titre’ will indicate that such a
transplant is likely to be able to proceed. Selecting ‘High Titre’ will indicate that this is
not likely to be possible and therefore relevant transplant survival information will not
be given. This field is only relevant when the nature of the incompatibility of the pair
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is blood group incompatibility and there is a ‘Not Applicable’ option that can be
selected if this is not the case.
HLAi Transplant with willing Donor: The clinician should decide whether, based on
HLA antibody levels, the pair could proceed with a HLA incompatible transplant in
line with the practices at that centre. Selecting ‘Low DSA’ will indicate that such a
transplant is likely to be able to proceed. Selecting ‘High DSA’ will indicate that this is
not likely to be possible and therefore relevant transplant survival information will not
be given. This field is only relevant when the nature of the incompatibility of the pair
is HLA incompatibility and there is a ‘Not Applicable’ option that can be selected if
this is not the case.
Recipient Age: Current recipient age (years), split into 5 groups: 18-30, 31-40, 4150, 51-60, 61+.
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Statistical Methodology for Chances of Transplant and Transplant
Survival Rate Estimation
Computing estimated chance of transplant
For the deceased donor waiting list, waiting times were calculated using existing data
from the national transplant database. Patients were selected that had characteristics
that were similar to those who have entered the National Living Donor Kidney
Sharing Scheme (NLDKSS). This gave us waiting times from the deceased donor
waiting list for a cohort similar to patients in the NLDKSS. This similarity was based
on variables that are relevant in the NLDKSS. These are blood group, calculated
reaction frequency and age. Cox proportional hazards models were then used to give
survival curves that can be interpreted as chance of transplant.
To estimate waiting time to transplant in the NLDKSS, simulations were used. The
simulations were performed in order to obtain more data than are currently available
as the scheme has only been in its current form since 2012. Data from pairs and
altruistic donors that have entered the scheme were selected randomly with
replacement to join the simulated scheme. Matching runs were performed that
simulated 3 years in the scheme, and this was repeated 10 times. Pairs could drop
out of the scheme with a fixed probability, and potential transplants could fall through
with a fixed probability that was based on the proportion of those that fell through in
the scheme. Registration time before first matching run and time to transplant after
identification of a potential transplant were selected at random from real data. Cox
proportional hazards models were then used to estimate time to transplant.
Computing transplant survival rates
A Cox proportional hazards model was used to determine the probability of transplant
survival for each patient based on their individual risk factor values. The estimates
were derived using data from the national transplant database. Transplant survival
looks at the survival of the graft and the patient until either graft failure or death.
Observations are censored if the graft is functioning and the patient is alive at the last
time point. The factors included in this model were recipient age group and transplant
type (deceased compatible, living compatible, living blood group incompatible and
living tissue type incompatible).
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