SIR Model Explorer

The Standardized Infection Ratio (SIR) is a primary summary measure used by the National Healthcare Safety Network (NHSN) to track healthcare-associated infections (HAIs) in U.S. healthcare facilities. The SIR metric ­provides comparisons between the number of observed infections in a facility to the number that were “predicted” to have occurred if the facility had rates equal to the rate of the national 2022 baseline. The number of “predicted” infections is calculated using regression models, also known as risk adjustment models. Different risk adjustment models exist for each outcome type and facility type.

View information about the variables used in SIR calculations under the 2022 baseline in the tables below. Refer to NHSN’s Guide to the SIR (2022 baseline) for more information about the SIR metric, including calculation of the number of predicted HAIs, model inclusion and exclusion criteria, and interpretation guidance.