STANDARDIZED INFECTION RATIO SIMPLIFIED Laurie Fish, RN, BSN, CIC.

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 group divided by the number of infections expected in that group, based on a standard population.

Observed (O) HAIs

Expected (E) HAIs

= SIR

This is the number of HAIs in your hospital

This is the estimated number for your hospital based on standard population

Standard Population for CAUTI is 2009

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Standard Population

Standard Population for CLABSI is 2006-

2008

How does my facilities performance compare?

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Making Comparisons

Your expected is determined using the

following formula:standard population

rate/1000 X your device days=

Expected

Your actual (observed) number is

then divided by your

expected=

SIR

How is the CLABSI SIR calculated?

The national rate of CLABSI for a teaching medical surgical unit is 2.1/1000 cath days

Org id

Location

Summary Yr/Half

Months

Infcount

Number expected

Central line days

SIR SIR P Value

95% Confidence Interval

10018

ICU 2009H1 3 2 1.785 850 1.12

0.5327

0.199-3.527

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?

Type of ICU # of CLABSI

# of central line days

CLABSI Rate

NHSN Rate

p value

Expected # of CLABSI

Medical Cardiac

2 380 5.26 2.0 0.09 0.76

Medical 1 257 3.89 2.6 0.15 0.67

Med/Surgical 3 627 4.78 1.5 0.11 0.94

Neurosurgical 2 712 2.81 2.5 0.32 1.78

Total 8 1976 4.05 4.15

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

• 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

1.2-2.0

0.7-1.5

0.1-0.5

0.5-1.2

0.5-1.5

Risk Adjustment: CLABSI and CAUTI

Population level risk adjustment:

1.Patient mix by type of unit location

2.Hospital affiliation with a medical school

3.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….

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Questions?