Hospital rankings and report cards are growing in number and importance, but a new University of Michigan study suggests these measures may be inaccurate if they don’t take into account the high number of very sick patients that large hospitals receive as transfers from other hospitals.

This study, which focused on medical intensive care unit (MICU) patients, was as much about benchmarking as it was about the MICU, says Andrew L. Rosenberg, MD, assistant professor of anesthesiology and internal medicine at the University of Michigan Health System (UMHS) in Ann Arbor, and lead author of the study.

“The idea of this study was to try to quantify something that most physicians intuitively know: Transfer patients are sicker,” says Rosenberg. “However, this is difficult to quantify because the type of precise data needed are often lacking; they are expensive and hard to get at. In fact, much of [the quality rating] benchmarking deals with administrative databases, not clinical databases.”

The UMHS study results were published in the June 3, 2003, issue of the Annals of Internal Medicine, in an article titled, “Accepting critically ill transfer patients: Adverse effect on a referral center’s outcome and benchmark measures.”

“We used a very detailed clinical database [APACHE III for Acute Physiology and Chronic Health Evaluation],” Rosenberg notes.

The study examined 4,579 consecutive admissions for 4,208 patients from Jan. 1, 1994, to April 1, 1998. A full 25% were transfer patients. Its measurements were MICU length of stay, hospital length of stay, MICU readmission, and hospital mortality rates. “We reasoned, why not study the place [MICU] where the most valid benchmarking tools are used?” says Rosenberg. “If we still can’t adjust for the ICU, how can we possibly do it at another level?”