For the roughly 15,000 Americans who need a liver transplant, it’s a waiting game. With demand for donated livers far outstripping supply, patients may spend months or years on a waitlist, their position gradually improving as they get sicker. A recent study suggests that this system may be changing, but not necessarily for the better.

To get or keep a good performance rating from the federal government, transplant centers have been labeling some patients “too sick to transplant” and dropping from the waitlist some who may have been viable candidates, the study found. The researchers also determined that, despite the centers’ actions, one-year survival rates for transplant recipients didn’t improve.

The study examined delisting at 102 liver transplant centers and looked at the cases of 90,765 waitlisted adults who died between 2002 and 2012.

Midway through that period, the Centers for Medicare & Medicaid Services implemented a new policy for transplant centers that participate in the Medicare program.

To meet CMS’s new performance standards, which the agency recently eased somewhat, liver transplant centers have to achieve certain survival rates. Centers that fall short may be required to revamp their programs or risk losing their Medicare funding. (In a letter last month about the guidelines, CMS noted that one-year survival for liver transplant patients increased from 87.7 percent in 2007 to 90.8 percent in 2014.)

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But something happened when the policy took effect in 2007: The percentage of patients that centers considered too ill or unsuitable for a transplant rose by 16 percent, and the likelihood that a candidate would be delisted continued to increase through the end of the study period. Compared with earlier, patients who were taken off the waitlist after the CMS policy change were more likely to be 55 or older and have more-severe liver illness.

The study’s authors speculate that the new standards made transplant centers more averse to risk and encouraged them to drop sicker patients who might negatively affect their survival statistics.

Some suggest there’s a different way to look at the impact of the CMS policy. “Maybe centers are making the internal decision of trying to choose the best candidates,” said David Goldberg, medical director for living donor liver transplantation at the University of Pennsylvania.

The most common reason for a liver transplant is cirrhosis, or scarring of the liver, often caused by hepatitis C or alcoholic liver disease.

The severity of patients’ illness is evaluated based on their Model for End-Stage Liver Disease (MELD) score, a number between 6 and 40 that predicts the risk of death within three months and is calculated based on three laboratory values.

Nationwide, 6,729 liver transplants were performed in 2014, but 1,821 patients died on the waitlist. Another 1,300 people were removed from the waitlist because they were considered too sick for a transplant.

“There’s no common definition for when someone is too sick to transplant,” said the study’s lead author, Natasha Dolgin, an MD/PhD candidate at the University of Massachusetts Medical School. Patients’ health may deteriorate to the point that a transplant is no longer advisable, for example, or they may contract an infection that makes delisting necessary. But those reasons don’t explain the increase in delisting following the introduction of the CMS policy, according to the study.

Still, Dolgin said, she doesn’t blame transplant centers for their waitlist decisions. Once there is a “benchmark, you try to meet that.”

Kurt Schnier, an economist at the University of California at Merced who has examined the impact of the CMS policy on kidney transplant practices, said the standards have lengthened the time patients are on the waitlist. (That research is under review for publication.) The CMS policy may also affect surgeon behavior at centers that don’t meet the standards, leading them to conduct fewer transplants, for example.

“It’s a well-intended policy,” Schnier said. “The problem is that it creates perverse incentives at the physician level that may undermine the personal welfare of the general population.”

“This is part of the culture now,” said Hillel Tobias, medical director of New York University’s liver transplant service and chairman of the medical advisory committee of the American Liver Foundation. “You can’t take a chance, because if your numbers go down, you’re going to get canned.”

One of the goals of the CMS policy was to improve outcomes, a goal prompted by concerns about quality and service at transplant centers. Yet the study found that the new standards didn’t have a statistically significant impact on mortality rates within a year of transplantation.

Liver transplants are complicated, and the fact that survival didn’t improve might reflect complications that are not preventable, Goldberg said.

Asked to comment on the study, a CMS official said the agency “is reviewing available evidence about the impacts of our policies on organ transplant centers. After thorough review we will determine a course of action.”

This column is produced through a collaboration between The Post and Kaiser Health News.