The Perfect Match: Dispelling the Myths About New Kidney Allocation Concept
And for those who insist that “first come, first served” is fair, Friedewald has a different opinion, calling it “a complete fallacy. The first come aren’t the first served. Some people won’t live long enough to wait for a kidney, if the line is too long. Everyone believes that a line is ‘first come, first served,’ because we’re used to delis and things like that, where you actually get served. But a lot of people aren’t getting served.”
That may never change, but the concepts outlined in the UNOS document aim to achieve an additional 15,223 life-years lived with a transplanted kidney for every year’s worth of deceased-donor transplants. How? Let’s explore.
How the System Would Change
Early on, Concepts for Kidney Allocation (available at optn.transplant.hrsa.gov/SharedContentDocuments/KidneyConceptDocument.pdf) outlines the flaws of the current system: “[I]t does not strive to minimize death on the waiting list nor maximize survival following transplant. It does not recognize that all candidates do not have the same ability to survive the wait. It does not attempt to match the characteristics of a donor’s kidney to the candidate’s characteristics to promote a long and healthy survival post-transplant. The system can be better, and it can be designed to achieve more in the way of health and longevity than it currently does.”
Aware of the problems, and with input from hundreds of individuals—including transplant professionals, recipients, and candidates, as well as donor families, living donors, and the general public—UNOS’s Kidney Transplantation Committee has spent six years (so far) developing goals for a new allocation system. The concept document delineates three key factors in achieving those goals:
• Utilizing a kidney donor profile index (KDPI), a continuous measure used to estimate the potential function of a donated kidney if it were transplanted into the average recipient, to better characterize donor kidneys.
• Allocating some kidneys (20%) by a combination of the KDPI and a candidate’s estimated post-transplant survival (EPTS).
• Allocating the majority of organs (80%) by age-matching so that candidates within 15 years older or younger than the donor are prioritized.
The KDPI is based on the characteristics of the donor, including age, race/ethnicity, height, and weight, and whether he/she had any of the following factors: hypertension, diabetes, hepatitis C, elevated creatinine level, a cerebrovascular cause of death, or cardiac death. It is important to remember that a score below 20% indicates a kidney with the predicted longest function; it’s like being in the top 20% of your graduating class.
A candidate’s EPTS is based on age, length of time on dialysis, diabetes status, and history of prior organ transplant. “While no calculation will be able to predict life expectancy with 100% certainty, these four factors provide a reasonable estimate for identifying those candidates who have the longest possible EPTS,” the committee writes.
Once a KDPI has been established, there are two scenarios for how a candidate might be selected. Kidneys with a KDPI of 20% or lower are allocated based on EPTS. Those with a KDPI of more than 20% are allocated based on age-matching within 15 years (older or younger) of the recipient’s age.
To use the examples given in the report: Let’s say there are three candidates for a kidney. Mary is 30, Sophia is 21, and David is 60. Along comes a kidney with a KDPI of 10%. Since Mary and Sophia have better estimated survival than David (EPTS, 19%, 12%, and 75% respectively; again, it’s the percentile, so lower is better), they would have priority for that kidney.
However, if the available kidney has a KDPI of, say, 40%, age becomes a bigger factor. If the donor is 34, Mary and Sophia continue to have priority over David, since recipients ages 19 to 49 would be considered first. If the donor is 55, however, David would have precedence over Mary and Sophia, since the age range for that kidney recipient would be 40 to 70.
All of this can be confusing, and it leads one to suspect that some of the news entities who misspoke either did not understand what they were reading or perhaps did not even finish reading the report. But these components do not even tell the entire story; they are exactly that, components. The final proposal, which will be written only when all the feedback from a public comment period has been compiled and analyzed, “will include all the details of who gets the kidney,” as Friedewald says.
What is important to know now is that “waiting time will continue to be a major part of who gets a kidney” if the revised allocation concepts become policy, Friedewald emphasizes. “What this document says is that we’re generally going to group people based on the quality of the donor kidney. But once we do that—let’s say it’s a top 20% kidney—well, then the top 20% of candidates who are expected to live the longest will be up for that kidney. But that may be 10,000 people. Which of the 10,000 people gets the kidney? The person who waits the longest.”
