The case for a population standardized infection ratio (SIR): A metric that marries the device SIR to the standardized utilization ratio (SUR)

Abstract

Background:The device standardized infection ratio (SIR) is used to compare unit and hospital performance for different publicly reported infections. Interventions to reduce unnecessary device use may select a higher-risk population, leading to a paradoxical increase in SIR for some high-performing facilities. The standardized utilization ratio (SUR) adjusts for device use for different units and facilities.Methods:We calculated the device SIR (calculated based on actual device days) and population SIR (defined as Σ observed events divided by Σ predicted events based on predicted device days), adjusting for the facility SUR for both central-line–associated bloodstream infections (CLABSIs) and catheter-associated urinary tract infections (CAUTIs) in 84 hospitals from a single system for calendar years 2016 and 2017.Results:The central-line SUR was 1.02 for 801,172 central-line days, with a device SIR of 0.76 and a population SIR of 0.78, a 1.6% relative increase. On the other hand, the urinary catheter SUR was 0.90 for 757,504 urinary catheter days, with a device SIR of 0.84 and a population SIR of 0.76, a 10.0% relative decrease. The cumulative attributable difference for CAUTI to a target SIR of 1 was −135.4 for the device SIR compared to −203.66 for the population SIR, a 50.8% increase in prevented events.Conclusion:Population SIR accounts for predicted device utilization; thus, it is an attractive metric with which to address overall risk of infection or harm to a patient population. It also reduces the risk of selection bias that may impact the device SIR with interventions to reduce device use.