The rate of patient deaths (mortality) in a hospital is shown as a mortality ratio that compares patients' actual mortality to their expected mortality.
The "observed-to-expected mortality" is a risk-adjusted measure of a hospital's mortality. This ratio is created from two sets of numbers:
- Observed mortality. The rate of patient deaths in the hospital each quarter.
- Expected mortality. The expected average of hospitalized patient deaths with a particular illness or condition that are beyond the control of the medical center, such as age, gender and other medical problems.
Observed mortality is divided by the expected mortality to create the O/E ratio.
The meaning of an O/E ratio depends on the score.
- Equal to 1.5. The hospital's mortality is higher than expected.
- Equal to 1.0. The hospital's mortality is equal to what is expected.
- Equal to 0.75. The hospital's mortality is 25 percent lower than expected.
- Equal to 0.50. The hospital's mortality is 50 percent lower than expected.
A lower score is better. Mayo Clinic has a target of 0.71.
* Observed-to-expected mortality
*Source: Vizient CDB/RM. Vizient is an alliance of academic Medical Centers and their affiliated hospitals.