Academic medical centers such as UK HealthCare including Kentucky Children's Hospital take care of the very sickest patients. That’s why patient survival rates are adjusted to account for just how sick the patients are when they come to the hospital, considering the seriousness of their illness plus complicating factors like age, obesity or chronic conditions.
Observed-to-expected mortality (death) compares two numbers:
- Observed mortality is the actual number of patients who died during a particular period. For example, 10 deaths among 1,000 patients would be a rate of 1 percent.
- Some people are so sick they are not reasonably expected to survive. More of these patients are seen at places like UK HealthCare because they are better equipped to help. Expected mortality adjusts for how sick patients are compared with patients seen at other hospitals in the United States.
To reach the final number, the observed rate is divided by the expected rate, meaning that the number of actual deaths is compared to how many people were so sick that they were not expected to live.
A score of 1.00 would mean exactly the same number of patients who might have been expected to die did in fact die.
A score higher than 1.00 means more patients died than were statistically expected to. For instance, a mortality index of 1.10 would mean 10 percent of people who were expected to survive, did not.
A score lower than 1.00 means that more patients survived than were statistically expected to. For instance, if the ratio is .75, it means that for every 100 people expected to die, only 75 actually did. Twenty-five of those very sick people survived.
These rates are figured by VIZIENT, an alliance of academic medical centers and their affiliated hospitals representing approximately 90 percent of the nation’s not-for-profit academic medical centers. VIZIENT performs risk-adjustment calculations for all hospitals and provides reports to the participating hospitals. These numbers are used by hospitals nationwide.