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Price of Privacy

The Value of Revealing Waiting List Information

Research by
Burhaneddin Sandıkçı

Burhaneddin Sandıkçı is assistant professor of operations management at the University of Chicago Booth School of Business.

Using the information contained in a waiting list can help patients in need of a donor liver make better decisions and live longer.

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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.