The SIR is a summary value used to track healthcare-associated infections (HAIs) at a national, state and local level. The SIR adjusts for several risk factors found to be significantly associated with differences in infection incidence. It can be used to track HAI prevention progress over time; lower SIRs are better.

The Centers for Disease Control and Prevention’s (CDC) adjusts the SIR for risk factors that are most associated with differences in infection rates. In other words, the SIR takes into account the fact that different healthcare facilities treat different types of patients. For example, HAI rates at a hospital with a large burn unit (where patients are at higher risk of acquiring infections) cannot be directly compared to a hospital that does not have a burn unit.

In HAI data analysis, the SIR compares the actual number of HAIs reported (observed by Infection Prevention Surveillance) with the baseline U.S. experience (predicted or expected).

SIR = Observed HAIs / Predicted or Expected HAIs

Aggregate data from the CDC’s National Healthcare Safety Network (NHSN) is used to calculate the risk-adjusted number of HAIs predicted or expected.

In Plain Language
Your data are compared to the average of a historical standard population, adjusted for risk.

The SIR is not a rate; it’s a value or ratio, comparing one number to another. It will only be calculated if the expected number of HAIs is greater than 1, because you can’t have less than a whole person infected.

Download this tip sheet to learn more about SIRs and what the value actually tells you. Also, learn more from the CDC’s HAI Progress Report: Questions and Answers.

atom Alliance works closely with providers to help reduce HAIs in hospitals. Learn more.