An infection preventionist presents hospital-wide CLABSI rate data for the last 12 months to the quality improvement committee. What would be the most appropriate statistical measurement for this type of infection data?

• A. Standardized infection ratio (SIR) per provider, unit, device, and procedure
• B. Incidence rate
• C. Relative risk
• D. Hazard ratio

Answer: (A)

When comparing hospital-wide CLABSI data, you want a measure that accounts for how much central-line use occurred and benchmarks against a standard expectation. The standardized infection ratio does exactly that by dividing the number of observed infections by the number predicted for that setting, using factors like unit, device days, and procedure mix. This yields a ratio that centers around 1.0, where around 1.0 means performance is as expected, above 1.0 signals more infections than expected, and below 1.0 indicates fewer. This standardization makes it possible to compare across units and time, even when device use or patient mix varies, and it aligns with how NHSN benchmarks are reported for CLABSI.

In contrast, a simple incidence rate—new infections per 1,000 device-days—describes the raw rate of infections but doesn’t compare that rate to an expected baseline. Without that benchmarking, differences in exposure or patient risk across units can mislead comparisons. Relative risk or hazard ratio come from different study designs and are used to compare risk between groups or over time within a cohort or time-to-event analysis, not for standardized, hospital-wide benchmarking of CLABSI data.