Q&A: Mortality rate, observed/expected

Q: Do you have any information about mortality rate, observed/expected, or can you direct me to where I might get additional information to better understand this metric?

A: The mortality index is defined by the number of patient deaths in a hospital within a ratio that compares actual deaths within a specific time period to expected deaths pulled from risk of mortality data. This is often referred to as the “O” (observed) to “E” (expected) death rate.

The O/E mortality rate is an example of a risk adjusted measure.

The observed mortality is represented by the actual number of patients that died in the hospital in a specific time frame (month, quarter, year etc.). The expected mortality is the average expected number of deaths based upon diagnosed conditions, age, gender, etc. within the same timeframe. The ratio is computed by dividing the observed mortality rate by the expected mortality rate.

The lower the score the better. For example, if the score is a one—it demonstrates that the actual mortality rate is equal to the expected rate. If the ratio is 1.25 it demonstrates the fact that more patients died than what might be expected. If the ratio is .75 it demonstrates that less patients died than were expected to.

This ratio can be affected by the quality of care provided and/or the quality of documentation captured in the medical record. If the CDI team does not help capture the highest severity of illness and risk of mortality appropriate for the physician or facility’s patient population through complete documentation, then the risk adjustment applied to this ratio will not be accurate. If the patient dies, it may appear as though the death may have been preventable.

Many CDI programs perform “death reviews” of these records to ensure that that the documentation clearly reflects severity of illness and risk of mortality. The goal of these reviews is to capture an APR-DRG (all-payer refined diagnosis related group) risk of mortality score of a 4. The higher level of risk of mortality demonstrates that there is a high probability of patient death.

There are a number of software programs that can compute the expected mortality of your patient population. Likely your quality department can assist you in in obtaining your  O/E ratio and help you identify the ratio for specific service lines (cardiovascular, neurosurgery, etc.), specific conditions (heart failure, specific surgical procedures etc.), or by provider.

Although there are many factors that can influence your O/E mortality ratio, it can be used to assess the effectiveness of your documentation improvement efforts as well. But we must ensure that the interpretation of this metric does take into consideration other possible influencing factors as well.

Editor’s Note: Laurie L. Prescott, RN, MSN, CCDS, CDIP, AHIMA Approved ICD-10-CM/PCS Trainer, and CDI Education Director at HCPro in Danvers, Massachusetts, answered this question. Contact her atlprescott@hcpro.com. For information regarding CDI Boot Camps visitwww.hcprobootcamps.com/courses/10040/overview.