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Let’s all agree about one thing: the basic problem with the present system for allocating deceased donor (DD) kidneys is the persistent shortage of kidneys from donors, both living and deceased. As a result, waiting times for a DD kidney can last years, and some transplant candidates die while waiting for the “gift of life.”
Recently, the United Network for Organ Sharing (UNOS), the organization that oversees the allocation of DD organs in this country, and the Organ Procurement and Transplantation Network (OPTN) published for public comment a document titled “Concepts for Kidney Allocation” that describes possible revisions to the DD kidney allocation system. Although the deadline for public comments (April 1, 2011) has passed, the document no doubt will continue to provoke discussion because it posits a fundamental change in the kidney allocation process.
The allocation concepts described in the document were developed by the OPTN/UNOS Kidney Transplantation Committee in response to perceived limitations in the current DD kidney allocation system. These limitations include: (1) higher than necessary discard rates of kidneys that could benefit candidates on the waiting list; (2) varying waiting times due to candidate blood group and geographic location; and (3) kidneys with long potential “lifetimes” being transplanted into (mainly older) candidates with significantly shorter expected lifetimes, and vice versa. A primary objective of a revised kidney allocation system would be to allocate kidneys with the greatest expected lifetimes to the candidates with the greatest expected lifetimes.
Before we look at the proposed changes, let’s quickly review the current kidney allocation system. The present system, in operation since the creation of UNOS in 1986, recognizes two types of DD kidneys: those from standard criteria donors (SCD) and those from extended criteria donors (ECD). ECD kidneys, which account for about 16% of all DD kidneys, have lower expected lifetimes than SCD kidneys, and are typically allocated to candidates who will accept an ECD kidney, typically older candidates.
The bulk of DD kidneys (84%) are SCD kidneys, and they are offered first to candidates on the local waiting list. The list is “order ranked”, primarily according to waiting time. So, generally speaking, the candidate who has been waiting the longest will be offered the DD kidney first.
Again, a problem with this system is that kidneys with potentially long lifetimes are sometimes transplanted into recipients with short lifetime expectations. Another problem with the present system is that ECD kidneys, which have shorter lifetimes but would be perfectly suitable for candidates with similarly shorter expected lifetimes, often are discarded instead of being transplanted. Why take an ECD kidney if your chances for an SCD kidney are almost as good?
The primary objective of the revised kidney allocation system would be to allocate kidneys with long expected lifetimes to candidates with similarly long expected lifetimes. In other words, as a candidate you would receive a kidney that “looks like you.”
To accomplish this goal, the revised system would utilize something called a “Kidney Donor Profile Index” (KDPI), which is a measure of a DD kidney’s quality and thus, expected lifetime. The revised system would allocate the highest quality kidneys – those in the top 20% – to the 20% of candidates with the highest “Estimated Post Transplant Survival” (EPTS). Ranking within this top 20% group might be based on waiting time, like the current system.
The remaining 80% of kidneys would be allocated to candidates who are within 15 years (older or younger) of the deceased donor’s age. In other words, a kidney that looks like the recipient (in terms of age). For example, if the deceased donor is age 50, then candidates ages 35 to 65 would be offered the kidney first. Again, ranking within this “age matched” group might be based on waiting time. If no one in the age matched group accepted the kidney it would be offered outside the age matched group.
The revised allocation concept document is prompting lots of discussion. That’s a good thing. Even better if the discussion reminds people of the desperate need for more organ donors and motivates them to become organ donors as a result.
Editor’s Note: The OPTN/UNOS “Concepts for Kidney Allocation” document may be viewed here.