Commentary from OPTN/UNOS Kidney Transplantation Committee Chair, John Friedewald

Related to Nikola’s post below on the proposed revisions to the deceased donor kidney allocation policy, Al Roth has posted some interesting commentary from OPTN/UNOS Kidney Transplantation Committee Chair John Friedewald (in response to a query on a list serve):

“The current proposal for kidney allocation from the UNOS kidney committee is what it is not because it was the first thing we thought of, and “wow, it’s perfect” but rather it is the product of 8 years of trial and error, consensus building, and compromise.  To state that EOFI takes into account both equity and efficiency would seem to suggest that the current UNOS proposal does not.  How could this be?  We have tried over 50 different methods of allocation and simulated them (which has not happened yet with EOFI).  And with each simulation, we view the results and how the system affects all sorts of different groups (NOT just age, but blood type, ethnic groups, sensitized patients, the effects on organ shipping, the effects on real efficiency in the system (the actual logistics).  And we have seen that some methods of allocation can generate massive utility (or efficiency in your terminology).  We can get thousands of extra life years out of the current supply of organs.  But in each instance, we have made concessions in the name of equity.  The current proposal does not increase or decrease organs to any age group by more than 5% (compared to current).   This has been our compromise on equity.  What we see in utility/efficiency is an extra 8000+ years lived each year with the current supply of organs.  So the current policy has done a tremendous amount to balance equity and utility.  And we have left thousands of life years lived on the table in the name of equity.  Now you may argue that we have not done enough in that regard, but rest assured, we have given equity hundreds of hours of consideration.
“In terms of the possible changes to living donor kidney transplant rates, we have to understand why there is concern.  The current “Share 35” plan prioritizes kidneys from donors under age 35 to pediatric candidates.  Because there are so few pediatric candidates in any area, they tend to have very short waiting times compared to adult candidates (months vs. years).  And so, when faced with the decision, a pediatric candidate can be fairly sure to get a high quality deceased donor kidney in a relatively short period of time.  So why take a kidney away from a living donor?  And so the argument goes.  Pediatric candidates will maintain their priority in the new system.  And in fact, may have even better organs, because Share 35 will now relate to KPDI rather than donor age alone, a better marker of kidney longevity (some kidneys from donors under 35 aren’t that great, but KPDI tends to look at more factors than just age and really get to kidney quality).  So I would expect that many pediatric candidates will still take a kidney from a deceased donor rather than a living donor.  The living donor kidneys would still often be predicted to last them longer, but there is the issue of the risk to the living donor to consider in that difficult equation.
“With adults, it will be quite different.  The new proposal would prioritize kidneys from donors with a KDPI < 20 (the “longest lasting” 20% of organs) to candidates with the 20% longest estimated post-transplant survival (EPTS).  This is done primarily to avoid extreme mismatches in donor and recipient longevity.  Why 20%?  There are several reasons.  First, the equations we use to predict EPTS are not perfect (nor could they ever be).  But it turns out, the EPTS prediction is much better at the tails than it is in the middle.  So we are pretty good at picking out the ones at the far left of the curve.  And 20% was chosen because the EPTS curve changes slope around that point.  And 20% is a round number (we could have chosen 17% or 23%, but that would even confuse people more – and we have heard over and over, “it can’t be confusing”.  The EPTS calculation was made simpler in response to public feedback.).  So the concern that I have heard is that if you are a candidate in the top 20% EPTS, then you will get a great kidney right away, and why would you take a living donor kidney? Just like the kids.  But the important difference here is in the numbers.  Given 92,000 patients on the wait list, there will be about 18,400 candidates in the “top 20%” EPTS group.  Now they will have priority (after multi-organ, after pediatrics, after zero mismatches, after previous live donors) for those organs, but remember, we only perform 11,500 or so transplant a year.  So the top 20% would be 2300 organs a year (assuming there are no pediatric, multi-organ transplants done).  So it is likely that candidates in the top 20 might wait years (longer than candidates in the bottom 80 EPTS would wait for a kidney in fact) for a top 20% kidney.  That is why top 20 EPTS candidates are eligible for all kidneys, because in practice, many of them will accept an offer from a donor with KDPI > 20%.  And guess what?  They have to wait JUST AS LONG for those as every other candidate.  So we are not really advantaging that top 20% group as much as people might think.  But we are trying to keep those really long lived organs for those who stand to benefit from them a long time.  And by doing that, we can realize all those extra life years lived.  And possibly decrease returns to the waitlist (which benefits all candidates indirectly).  We think that has to be worth some tradeoffs.  We have given careful thought and consideration to those issues.
“Thanks for listening (reading), and we really appreciate all the interest in the proposal.  I just want to make sure we are all talking about the same set of facts.

John Friedewald.

 

The Petrie-Flom Center Staff

The Petrie-Flom Center Staff

The Petrie-Flom Center staff often posts updates, announcements, and guests posts on behalf of others.

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