This is a continuation of yesterday’s blog post on why national kidney exchanges are not reaching their full potential.

In yesterday’s post, we described how a single national kidney exchange would be efficient. By having a large pool of candidates, it will lead to both more matches and faster matches. But we observe some hospitals do not join an exchange. And even hospitals that do join an exchange still perform some or most of their matches in-house. Below are some reasons. Part 3 will outline some solutions.

Hospitals believe they will get more transplants doing swaps in-house

Everybody wants to do what is best for the patients. However, that is hard to know what that is in practice. Hospitals want to do what is best for their own patients, the ones they know and care for. It is difficult for doctors at a single hospital to judge what is collectively best for all the patients in the U.S. One of the problems facing a kidney exchange is that maximizing the number of transplants in the pool may not maximize the number of transplants within a hospital that is a member of the exchange.

Let’s say there are two transplant hospitals A and B. Hospital A has 3 pairs in its pool and can match all 3 of them. Hospital B has 4 pairs and can match 2, for a total of 5 transplants as shown below. Black lines show matches used while orange lines show matches that are not used.


Five transplants when hospitals don’t cooperate. Graphic based on Nat. Bureau Econ. Res.

Now let’s combine the pairs from the two hospitals in an exchange. If we do so, we find we can get a total of 6 transplants as shown in the figure below.


Six transplants when hospitals cooperate. Graphic based on Nat. Bureau Econ. Res.

Hospital B goes from 2 transplants to 4. But notice that Hospital A drops from 3 transplants to 2. The patient in Pair A1 no longer gets a kidney and Hospital A performs one fewer profitable transplant. Hospital B and patients in pair B1 and B2 benefit at the expense of Hospital A and the patient in Pair A1. Thus, Hospital A has an incentive to withhold its pairs from the exchange and perform the swaps in-house.

If every hospital performs all the easy matches in-house, then the exchange will contain fewer pairs. This will make finding matches harder. Even worse, the exchange will only contain hard-to-match pairs, making it even less likely that patients in the exchange will find a match. Hard to match pairs will be patients with O blood type (for more see this Mar 2010 blog post) and patients with high levels of antibodies to human leukocyte antigens (for more see this Feb 2011 blog post.)

Note that most hospitals may not even realize that they are withholding pairs from the exchange. If a patient and donor match (which is likely if the donor is blood type O), the hospital will just proceed with the transplant without even considering entering them into an exchange. By transplanting their easy-to-match O donor pairs directly, they leave the national pools with a surplus of O patients and a shortage of O donors.

Hospitals believe there is less delay doing swaps in-house

Another reason hospitals may prefer to handle swaps in-house is the perceived high administrative cost and delay caused by placing patients in an exchange.

For example, the United Network for Organ Sharing (UNOS is the national organization responsible for the distribution of deceased donor kidneys) has started a pilot program to create a national living donor kidney exchange. It taken over two years to develop a consensus of how to operate the program. Finally, in November of last year it conducted its first match run which found 3 sets of matches. Only one of them was accepted and resulted in 2 transplants. Since then it has not had a single match offer accepted and no further transplants have occurred. (See Jan 2011 blog post for details.)

Hospitals are quickly learning that a majority of offers made by the national exchanges do not lead to a transplant. With a lack of success in a national exchange, hospitals would be negligent to not try to help their patients by conducting matches within their own patient pools or form small regional pools.

Here’s an explanation why I think match offers may not lead to a transplant. Imagine a swap that involves three sets of patients-donor pairs. For each of the three transplants, the surgeon has to approve of the donor. If any one is rejected, then the entire swap fails. Then all transplant pairs require a cross-match test for compatibility. Again, if any one fails or cannot be completed within the required time limit, then the swap fails. Finally, all six surgeries must be scheduled. If any of surgeries cannot be scheduled within the required time windows, then the swap will fail. If each of the 3 step for each of the 3 transplant has a 7% chance of failure, then the cumulative chance of success for a 3-way swap is only about 50 percent (1 – 0.07)^9 = 0.52.

All of the steps above are easier to coordinate if they are conducted within a single hospital. An important key to success for a national exchange is to remind every transplant center how important it is to get the approvals and tests completed in a timely manner and to drive these transplants to completion.

Hospitals believe there are lower medical risks doing swaps in-house

Finally, some hospitals fear that participating in an exchange will expose them to higher risk donors. Each hospital does a very thorough examination of donors prior to accepting them into the transplant program. Accepting a donor that they did not evaluate exposes them to two risks, one real and the other perceived.

Let’s cover the perceived risk first. A surgeon at the transplant hospital probably believes the evaluation of donors done at her hospital is excellent and trusts all members of the transplant team. However, in an exchange, the donor comes from another hospital. The surgeon may not personally know the evaluation team at the donor hospital. She may not be familiar with the evaluation criteria used at that hospital. In fact she may believe that the testing done there may not be  is not as rigorous as its own.

I believe that this concern will be alleviated over time as hospitals become more comfortable with the concept of cross-hospital exchanges. There are only 268 transplant centers in the U.S. and most of them use a very similar criteria when evaluating donors. Even if the hospitals use different criteria for acceptance, the equipment they use are very similar so the test results themselves should be comparable across hospitals.

The real risk is that a patient and her surgeon may be subjected to is that the donor hospital may not be as careful in evaluating a donor in an exchange, knowing that it will not be responsible for the outcome of the transplant. This type of risk is known as moral hazard. It is one of the factors that led to the recent financial crisis. Banks reduced the effort made to ensure mortgages were properly evaluated when they knew they would not be responsible for losses caused by any future loan defaults. This is a real risk and has to be managed. One solution is to make sure a certain percentage of matches made in the national exchange include pairs in the same hospital. This should encourage hospitals to do a good job of evaluating donors, since they won’t know which transplants will remain in-house.

In addition to donor evaluation risk, accepting a kidney from another hospital also entails transportation risk. Performing a transplant completely within a single hospital means that the kidney travels a few feet between the donor and the recipient.

The trauma a kidney undergoes is divided between warm ischemia time (the time it takes from when blood stops flowing to the organ to the time it is packed in ice) and cold ischemia time (the time it takes to transport the chilled organ from donor’s operating room to the recipient’s operating room and reattach it). The warm ischemia time causes the most damage. It will be a few minutes and it won’t differ whether a kidney is recovered within the same hospital as the patient or in a different one. The cold ischemia time for an in-house exchange can be as short as 10 to 15 minutes. However, if the donor operation takes place in New York while the transplant operation is in Los Angeles, the cold ischemia time may be as long as ten hours if there are flight delays.

Some transplant centers will not accept live kidneys that have been transported by air. I believe this is an unnecessary restriction. All transplant centers accept deceased donor kidneys recovered from outside their hospital. These kidneys are often delivered by commercial or charter aircraft, sometimes with cold ischemia times of over 20 hours. (For more on shipping kidneys, see this Dec 2010 blog post and an upcoming blog post.)

The third and final blog post provides ideas to solve these issues.