Because Dartmouth’s analysis focuses solely on patients who have died, a case like Mr. Putrus’s would not show up in its data. That is why critics say Dartmouth’s approach takes an overly pessimistic view of medicine: if you consider only the patients who die, there is really no way to know whether it makes sense to spend more on one case than another.

According to Dartmouth, Medicare pays about $50,000 during a patient’s last six months of care by U.C.L.A., where patients may be seen by dozens of different specialists and spend weeks in the hospital before they die.

By contrast, the figure is about $25,000 at the Mayo Clinic in Rochester, Minn., where doctors closely coordinate care, are slow to bring in specialists and aim to avoid expensive treatments that offer little or no benefit to a patient.

“One of them costs twice as much as the other, and I can tell you that we have no idea what we’re getting in exchange for the extra $25,000 a year at U.C.L.A. Medical,” Peter R. Orszag, the White House budget director and a disciple of the Dartmouth data, has noted. “We can no longer afford an overall health care system in which the thought is more is always better, because it’s not.”

By some estimates, the country could save $700 billion a year if hospitals like U.C.L.A. behaved more like Mayo. High medical bills for Medicare patients’ final year of life account for about a quarter of the program’s total spending.

Under the House health care legislation pending in Congress, the Institute of Medicine would conduct a study of the regional variations in Medicare spending to try to determine how to reward hospitals like Mayo for providing more cost-effective care. Hospitals identified as high-cost centers might even be penalized, perhaps receiving lower payments from the government. The Senate bill calls only for studies of Medicare spending variations, so it will be up to House-Senate negotiators to resolve the matter in the final legislation.

That prospect worries Dr. Rosenthal and his U.C.L.A. colleagues, who say that unless the distinction can be clearly drawn between excellence and excess in medical care, efforts to cut wasteful spending could be little more than blunt rationing.