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here are far more patients in the United States
waiting to receive a liver than there are donors.
But even though transplantation is the only viable
option available for end-stage liver disease, many patients
and their doctors reject livers that are offered to them
in the hope of getting a better one in the future. In fact,
almost half of all offered livers are reportedly rejected by
the first surgeon to whom the offer is made.
Patients have a legal right to reject a liver without
penalty; that is, past rejections are ignored and do not
affect the patient's rank in a prioritization system run by
the United Network for Organ Sharing (UNOS). The system
generates a waiting list that ranks patients according to
the severity of their disease, their location, and blood type
compatibility between the donor and the potential recipient,
among other factors. When a liver becomes available,
UNOS notifies the patient at the top of its waiting list.
The patient together with his or her team of doctors then
decides whether to accept the liver mostly based on the
health of the patient, the quality of the donor's liver, and
the likelihood of another offer in the future.
Knowing how soon another liver will be offered if the
current one is rejected is a critical component of that decision.
Patients could make the mistake of rejecting a liver
if another one will not be available for a long time, which
exposes them to the risk of death while waiting for the next
offer. Accepting a lower quality liver for fear of waiting too
long for another one, on the other hand, foregoes the possibility
of a higher quality liver in the future. They could
avoid such mistakes if the characteristics of other patients
on the waiting list were known, so that they can get a better
idea of their chances of receiving another offer. However,
detailed information on the composition of the waiting list is
unavailable to the public because of several issues including
privacy concerns.
This privacy may come at a very high price, according to
a recent paper by Chicago Booth professor Burhaneddin
Sandıkçı Lisa M. Maillart, Andrew J. Schaefer, and Mark S.
Roberts of the University of Pittsburgh; and Oguzhan Alagoz
of the University of Wisconsin. In a study titled "Estimating
the Patient's Price of Privacy in Liver Transplantation," the authors
compare what a patient would do upon receiving an offer
with and without a transparent waiting list, to find out if the
lack of information results in making poor decisions.
The authors find that patients benefitted tremendously
from a more transparent waiting list. A patient's average
life expectancy increased by about 4 to 5 percent, and it
could be much higher depending on the severity of the
disease, the age of the patient, and where the patient
lives. "If we completely ignore the information contained
in a waiting list, then we are doing a poor job of helping
patients make the best decisions," Sandıkçı says.
Decision Points
To understand how a patient's choices can change with
more information, the authors looked at how their sample
of 200 patients would make the decision to "wait" or
"transplant" given what the patients know about the quality
of the liver offered to them, their own health, and the composition
of the waiting list.
The study finds that the healthier the patient and the
more inferior the quality of the offered liver, the more
likely it is that he or she will wait for another offer. Sicker
patients tend to be less selective even if the quality of the
offered liver is low. Moreover, the likelihood of accepting
an offer is smallest when the patient is at the top of the
waiting list and gradually grows as his or her position on
the list deteriorates. In other words, patients are pickier if
they are near the top of the list and become less selective as
their rank decreases.
The authors then compared these results with those of
another study that ignored the information contained on
the waiting list. In this case, patients' decisions to accept
or reject is based only on the quality of the offered liver and
their own health, and not on the characteristics of the other
patients on the list.
As expected, there is less variation in patients' decisions
to accept or reject an offer when they have fewer factors to
consider. Patients are more likely to wait if they know that
they are close to the top of the list than if they did not know
their rank relative to the other patients. However, they
would probably accept a lower quality liver if they knew
they were close to the bottom. "The waiting list information
can change the decision of patients," says Sandıkçı.
Without knowing how they rank on the waiting list, patients
could make the mistake of waiting too long or not waiting
long enough for the best possible liver they can get to maximize
their life expectancy.
The Price of Privacy
To protect the identities of
patients waiting to receive a liver,
detailed information regarding
the characteristics of these
patients is not available to the
public. However, the authors
argue that a lack of transparency
results in significant loss to patients trying to decide
whether to accept a particular liver because they are unable
to make the best decision. They call this loss the "price
of privacy."
To estimate the price of privacy, the authors calculated
the amount of life days that a patient would gain if he or she
decides on an offer based on full knowledge of the waiting
list, as opposed to making a decision without this information.
The idea is that patients are expected to live longer
if a more informed decision helps them to make a better
choice about whether to accept an offer.
The study finds that a patient's average life expectancy
could go up between 4 and 5 percent. "The physicians we
talked with found this number amazing, especially considering
that billions of dollars of federal money are being
spent to boost life expectancies by about half of what we
find," says Sandıkçı.
Some patients benefited by as much as 15 percent while
others as little as 0.3 percent. Patients with more severe
diseases such as hepatitis B and C and those with acute liver
failure tend to have smaller gains. It seems that information
contained in waiting lists is more valuable for patients
with less debilitating diseases. Similarly, younger patients
tend to benefit more if they know the characteristics of
other patients waiting for a liver. This makes sense because
healthier and younger patients also are more likely to have better outcomes after a liver transplant, and so they have a
better opportunity to further their gains.
The price of privacy also is higher for those who live
in larger and more densely populated areas. Waiting list
information is more valuable in these regions because the
more patients there are in a certain area, the harder it is to
figure out their position on the waiting list. "Without this
information, patients are completely left in the dark," says
Sandıkçı. A more rural area, by contrast, will likely have
fewer patients and less competition, which makes it easier
to assess the likelihood of receiving another offer.
Imperfectly Fine
With the advent of internet technology, UNOS recently
began publishing some details on the composition of its
waiting list in order to strike a balance between privacy
and transparency. For instance, in this current system, a
MELD (Model for End-Stage Liver Disease) score from
6 to 40 is given to each patient waiting for a liver, where
higher scores indicate a more severe liver condition. UNOS
does not reveal the MELD score of each patient but instead
discloses how many patients belong to a particular range of
MELD scores. For instance, there could be 10 patients out
of 100 with a MELD score greater than 25 waiting for a liver
in a particular area.
While this type of information is far from complete,
Sandıkçı and his coauthors acknowledge that significant
technical and privacy issues could prevent the theoretical
ideal of full information from ever being achieved. This
led them to question whether such an ideal is necessary or
if the recent change in UNOS's policy of disclosing some
waiting list information is sufficient to help patients make
the best decisions.
The researchers explore this question in another study
and find surprising results: A completely transparent policy
adds no benefit to UNOS's current practice of publishing
partial information. Thus, revealing at least some information
about the composition of the waiting list can be very
valuable in helping patients make the right choices. "We
have evidence to argue that there's no reason to go through
the pain of publishing perfect information," Sandıkçı says.
"Estimating the Patient's Price of Privacy in Liver Transplantation." Burhaneddin Sandıkçı, Lisa M. Maillart, Andrew J. Schaefer, Oguzhan Alagoz, and Mark S. Roberts. Operations Research, November-December 2008. |
