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STANDARDIZED INFECTION RATIO SIMPLIFIED. Laurie Fish, RN, BSN, CIC. Standardized Infection Ratio. The SIR is a summary measure used to compare the HAI experience among one or more groups of patients to that of a standard population .
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STANDARDIZED INFECTION RATIO SIMPLIFIED Laurie Fish, RN, BSN, CIC
Standardized Infection Ratio • The SIR is a summary measure used to compare the HAI experience among one or more groups of patients to that of a standard population. • Groups can be in various units of measure (unit, hospital, state or country) • The data in the group is aggregated into a summary measure and then compared to the standard population
Definition of SIR The number of observed infections in an index groupdivided by the number of infections expected in that group, based on a standard population. Observed (O) HAIs Expected (E) HAIs This is the number of HAIs in your hospital = SIR This is the estimated number for your hospital based on standard population
Standard Population Standard Population for CAUTI is 2009 Standard Population for CLABSI is 2006-2008
How does my facilities performance compare? What is the relative difference in HAI occurrence between my facility compared to a common benchmark or referent period (standard population) This is the question the SIR answers for us.
Making Comparisons Standardpopulation Index group (your facility) Your actual (observed) number is then divided by your expected= SIR Your expected is determined using the following formula: standard population rate/1000 X your device days= Expected
How is the CLABSI SIR calculated? The national rate of CLABSI for a teaching medical surgical unit is 2.1/1000 cath days Hospital A Data: The E for ICU = (2.1/1000) X 850 = 1.75 SIR = 2/1.785 = 1.12
Expected less than 1 If the expected is less that 1, a SIR will not be calculated. If the expected is less than 1 your denominator is too low to calculate a precise SIR
How is SIR Calculated at hospital level? Overall CLABSI SIR= Observed/Expected= 8/4.15=1.93
Interpretation of the SIR • During the first 6 months of 2012, there was 1 CLABSI identified in our facility and we observed 2945 catheter days. • Based on the 2006-2008 data we expected 4.442 CLABSIs • This results in a SIR of 0.225 (almost 80% better than expected) • The p value and 95% confidence interval indicates the number of observed is not significantly lower that expected.
Interpretation of statistical tests Tip: The expected is one so it is significant if this range does not contain 1. • p value: <0.05 is considered statistically significant • Confidence Interval: if the range between the 2 numbers does not contain 1 the value is considered statistically significant. SIR Value of 1 0.5-1.5 1.2-2.0 0.7-1.5 0.1-0.5 0.5-1.2
Risk Adjustment: CLABSI and CAUTI Population level risk adjustment: • Patient mix by type of unit location • Hospital affiliation with a medical school • Bed size for the patient care location
Risk Adjustment for Surgical Site Infection Includes only deep and organ space and are detected through readmission to the same hospital • Colon: Age, ASA, duration, endoscope, medical school affiliation, bed size, wound class • Abdominal hysterectomy: Age, ASA, duration of procedure, hospital bed size
The SIR is not…. “The SIR is NOT intended as a comprehensive and conclusive HAI measure for all users and users of HAI data.” “More specific data at the state and local level are needed to target specific HAI problems and monitor the impact of prevention programs.”