Systems for Comparing Actual and Predicted Mortality Rates: Characteristics To Promote Cooperation in Improving Hospital Care

Mortality rates have been increasingly proposed as a measure of quality of hospital care. However, in themselves, mortality rates, whether used alone or in conjunction with severity-adjusted predicted rates, will not improve care. Only appropriate responses to mortality rates by clinicians, hospital administrators, consumers, and health care payers will improve care. For severity-adjusted mortality predictors to have their desired effect, they must have characteristics attractive to all of these groups. These characteristics are listed in this editorial.

During the past decade, mortality rates have been increasingly proposed as a measure of quality of hospital care. In 1986, the federal government released hospital mortality rates for Medicare patients in order to allow hospitals and consumers to evaluate care [1, 2]. These now-yearly releases include each hospital's mortality rates for 17 broad diagnostic groups, along with the expected mortality rates based on the group's severity of illness as assessed from Medicare reimbursement claims. For example, if a hospital's cardiac patient group has a severity-adjusted actual mortality rate of 15%, then a predicted rate of 5% could suggest suboptimal care, whereas a predicted rate of 30% would reflect outstanding care. Such comparisons of actual and severity-adjusted predicted mortality rates should facilitate hospitals' assessment of their own performance as well as permit fair comparisons among hospitals.

Unfortunately, because the Medicare predicted mortality rates have very limited adjustments for severity of illness within given diagnostic groups, it is difficult to say that differences between a given hospital's actual and predicted mortality rates are in fact related to quality of care [3-5]. Indeed, there is consensus in the health care industry and among researchers that if such data are to be used, they must be accurately risk adjusted. Over the years, several other mortality predictors have been developed that include far more detailed severity …