Medicare administrator William L. Roper and Sen. John Heinz (R-Pa.) clashed yesterday over Heinz's charges that hospitals are sending Medicare patients home prematurely because of the new Medicare prospective payment system.

At a hearing of the Senate Finance Committee, Heinz said Medicare patients go home "quicker and sicker" these days because hospitals are being paid a flat rate per stay under the new system, which started in fiscal 1984.

Under the prospective payment system, the Medicare payment is not reduced if the patient leaves the hospital quickly and it is not increased if the patient must stay longer than anticipated or receive extra tests. The main purpose is to get hospitals to discharge patients as soon as medically appropriate instead of letting them stay for a few extra days' rest or because it is inconvenient for the family to take them home immediately.

Before 1984, hospitals billed Medicare for all costs, limited only by Medicare's definitions of what fees were "reasonable" and "customary" for each procedure, taking into account prevailing local charges.

Roper did not deny that the new system has led to a reduction in average lengths of stay. But he told the Finance Committee he does not believe that the number of premature discharges of patients who are genuinely ill has increased substantially in recent years.

"That's just a guess," snapped Heinz. "The fact is you have no idea." He released a General Accounting Office report concluding that Medicare's "numerous studies" on prospective payment are not adequately designed to demonstrate the new system's impact on care.

Heinz said that in a case uncovered by his Senate Committee on Aging, an 85-year-old woman discharged after 12 days was sent to a "substandard nursing home" and died 14 hours later.

However, testimony by health policy analysts suggested that not enough information is yet available to determine whether Heinz's overall charges are true. Gerard Anderson, an associate professor at Johns Hopkins University, said that so far, "None of the indicators suggest that quality of hospital care or access to hospital care has deteriorated substantially as a result of prospective payment." Mark Chassin of Rand Corp. said, "We do not know whether . . . anecdotal reports represent the tip of an iceberg or an ice cube floating on the surface of the ocean."

The American Society of Internal Medicine said 200 of 246 members who responded to an admittedly nonscientific survey listed specific cases where they believed that the new system had led to poor quality of care. One doctor was quoted as saying, "Our efforts at the present time are simply to get the patients over 65 out of the hospital as soon as possible . . . . "

The American Medical Association said its own monitoring project as of May 15 had received responses representing approximately 8,050 physicians. It found that 66 percent of the responses said quality of care had deteriorated overall; 43 percent noted pressure to discharge patients early.

Roper pledged an all-out effort to block any inappropriate discharges in the future, including a conference next fall on ways to measure quality of care.