The busiest hospitals may not be the best

People trying to determine where they’ll get the best medical care have often been steered toward hospitals that treat large numbers of patients with similar problems. The rationale was simple: These centers have more experience, so they must be better at keeping you alive. In other words, practice makes perfect.

A considerable amount of research has reinforced that thinking, leading insurance companies and federal health officials to use patient volume as a barometer of medical quality.

But a pair of new studies challenges that practice. Whether you’re facing cardiac bypass surgery or trying to decide where your tiny premature baby would get the best treatment, patient volume alone isn’t a reliable predictor of care, according to the studies in the current Journal of the American Medical Assn.

Using the Society of Thoracic Surgeons’ cardiac surgery database, researchers from the Duke Clinical Research Institute in Durham, N.C., studied 267,089 cardiac bypasses performed at 439 U.S. hospitals in 2000-01.

In general, the more procedures the hospital did, the better the survival rates. But that wasn’t always true for patients younger than 65 and those considered at low surgical risk. The experience of the cardiac surgeon also influenced survival.

Many low-volume hospitals had low mortality rates, the researchers found, and many high-volume hospitals had higher-than-expected death rates.

In the second study, economist Jeannette A. Rogowski and research colleagues at the Arlington, Va., office of the Santa Monica-based Rand think tank reviewed the records of 94,110 babies, each weighing less than 3 pounds, who were born at 332 Vermont hospitals with neonatal intensive care units from 1995 to 2000. Units that treated larger numbers of babies with very low birth weights didn’t necessarily have the best survival rates.

A better indicator of where a baby was most likely to survive came from looking at the average mortality rate from several preceding years, Rogowski wrote.

Elizabeth McGlynn, associate director of Rand Health in Santa Monica, said both studies confirm that, on average, you can expect better outcomes at high-volume hospitals, but that volume alone is misleading.

Patients and insurers would do better to compare mortality rates adjusted to reflect that some hospital units treat sicker, older, higher-risk patients who are more likely to die and that others treat only a few patients each year, McGlynn said. Californians, she added, have had access to such information for bypass surgery since 2001.

Many insurance plans steer patients to high-volume hospitals, where they have smaller co-payments or deductibles, she said. Now those plans are asking whether that leads to the best care, she said.