Key Concepts
Prognosis matching
Prognosis matching is an approach to kidney allocation whereby we seek to prioritise the allocation of kidneys with a favourable prognosis to recipients with a favourable prognosis, and vice versa. Alternatively put, prognosis matching attempts to match the expected lifespan of the kidney with expected lifespan of its recipient.
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Prognosis matching has 3 main goals:
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Maximise the benefits (in terms of life years saved) from the highest quality kidneys by allocating these to recipients who are expected to benefit the most from them (i.e. recipients with the longest expected life-span post-transplant – typically younger)
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Avoid allocating kidneys with a very favourable prognosis to recipients with a poor prognosis (i.e. recipients with the shorted expected life-span post-transplant)
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Prioritise allocation of kidneys with a poor prognosis to recipients who might benefit from them, who would be willing to accept a lower quality kidney in exchange for reduced time on dialysis.
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The extent of the prognosis match between a donor and recipient is determined by the difference in the recipient EPTS and donor KDPI scores. A low EPTS score indicates a recipient with a favourable prognosis; a low KDPI score indicates a donor with a favourable prognosis. The closer in value the KDPI and EPTS scores, the better the prognosis match, i.e.:
EPTS 1, KDPI 1 = excellent prognosis match
EPTS 15, KDPI 40 = OK prognosis match
EPTS 20, KDPI 95 = bad prognosis match
The new kidney allocation system puts greater emphasis on prognosis matching compared to the current Australian kidney allocation system. Figure 3 shows the outcome of this change in terms of the extent of the correlation between KDPI and EPTS values in the two systems.
Simulated prognosis matching outcomes, current vs new algorithm
Immunological matching
Your immune system uses human leucocyte antigens (HLA) to determine which cells belong in your body, and which do not. HLA matching is performed prior to kidney transplant to establish whether a kidney is a good match or not.
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A good HLA match reduces the risk of graft loss. It also prevents the development of antibodies that would sensitise against future transplants.
We give priority in allocation to immunological matching because:
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A good immunological match is relatively rare, so is given priority when one is found
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For younger patients who need a second transplant, avoiding sensitisation is important.
Sensitisation
Sensitisation is the prior exposure to non-self HLA. It can occur due to prior transplantation, blood transfusions and/or pregnancies.
Screening for HLA antibodies is performed using a panel reactive antibody (PRA) test. A high PRA% means a high percentage of donors will be unacceptable to the recipient because of the presence of circulating antibodies that will react with one or more of the donor’s HLA antigens. For example, a PRA of 80% indicates that 80% of donors will be unacceptable to that recipient.
For very highly sensitised patients (i.e. PRA 95% and above), finding any acceptable match is difficult, therefore the highest priority is given when one arises