NOSOCOMIAL INFECTION

SURVEILLANCE METHODS

Masud Yunesian,M.D., Epidemiologist

Definition

• A dynamic process of gathering, managing,

analyzing and reporting data on events that occur in a specific population

Importance : SENIC study:

• Surveillance was the only component essential for reducing SSI, Pneumonia, UTI, & bacteremia.

• Other essential components:

– Sufficient no. of trained infection control staff and A system for reporting infection rates of SSI to surgeons.

Steps in surveillance:

• Definition of the event(s).• Systematic collection of data.• Summarization of data.• Analysis & interpretation.• Consuming the results for

improvement.

Purposes of the surveillance-1

1. Reducing the infection rate within a hospital.

2. Establishing endemic (baseline) rates.

3. Identifying outbreaks.

Purposes of the surveillance-2

4. Convincing medical staff.5. Satisfying regulators.6. Defending malpractice claims.7. Comparing infection rates

among hospitals.

Surveillance methods-1

1.Concurrent

2.Retrospective

Concurrent

• Flexible,• Informative • Timely • Capable of cluster detection• Capable of changing behavior• But expensive

• Depends on completeness, validity & accuracy of existing data.

• Does not identify problems as promptly as concurrent does.

• But isn’t expensive.

Retrospective

Surveillance methods-2

•Active :• accurate

• complete

• expensive

•Passive :• misclassification

• underreporting

• lack of timeliness

• less expensive

Surveillance methods-3• Hospital wide.• Periodic.• Targeted.• Defining the threshold limit.• Post discharge.

Hospital wide surveillanceSources of data:

1. Daily reports of microbiology labs.

2. Medical records of febrile patients.

3. Medical records of patients taking antibiotics.

4. Medical records of isolated patients

5. Daily interview with nurses & patients

6. Periodic review of autopsy reports

7. Periodic review of medical records of staff.

Periodic surveillance(S.):Hospital wide (H.W.S) during

specified periods,

And ,– Targeted S. during alternate periods

Or ,– Rotating H.W.S. from one unit to another

Targeted surveillance• Focuses its effort on :

– Selected geographic area (e.g. ICU)

– Selected service (e.g. cardio thoracic surgery)

– Specific populations of patients or infections:• At high risk of acquiring infection ( e.g.

transplantation)

• Undergoing specific interventions( e.g. dialysis)

• At specific site (e.g. blood stream)

Characteristics of targeted S.

• High accuracy & efficiency .• Incapable of detecting other

infections .• Criteria for selection of target :

– Frequency.– mortality & morbidity .– Cost.– preventability.

Defining the threshold limits

Case finding issues• Total chart review (standard method).• Laboratory reports.• Clinical ward rounds (twice a week).• Kardex screening (once or twice a week).• Fever chart.• High risk patients (transplant, diabetic,

leukemia, invasive methods, .. )

Analysis-1• The data should be analyzed.

• The analysis should be done by staff engaged in surveillance.

• Staff should decide how frequently to analyze the data:

– Frequently enough to detect clusters promptly.

– Collecting the data for a long enough period of time for changes to be meaningful.

Analysis-2

Numerator & Denominator

Overall rate =

No. of NI

Total no. of admitted or discharged patients

Adjusted rates

• For severity of illness.

• For length of stay.

• For exposure to device (e.g. ventilator)

Essential numerator data:

• Demographic :– name, age, sex , service, ward,admission

date, hospital identification number .

• Infection :– onset date , site of infection.

• Laboratory :– pathogen antibiogram

Numerator data : Risk factors“only when these data used for

analysis”

• An example for SSI:

• Kind of surgery.

• Date of surgery.

• Duration of surgery.

• Type of wound (clean ,dirty, …).

• Date of discharge.

Denominator data: Total no. of admitted or discharged pts.

OR No. of days of exposure :

– Total no. of pts. & pt-days in the unit,– Total no. of ventilator days,– Total no. of central line days,– Total no. of urinary catheter days.

Comparing rates necessary assumptions:

• Same definitions.• Same methods of S. & case finding.• Same accuracy of methods & personnel.• Same characteristics of hospitals/wards:

– Length of stay,– Risk indices,– exposure to devices,– ...

“Dissemination” “Surveillance is not complete

until the results are disseminated to those who use

it to prevent and control”

dissemination - continued

• Confidentiality must be regarded • Regular time intervals for

reporting .• Format of reports :

–Summary , table , graph

Evaluation• At least annually ask yourself :

– Did the system detect clusters ?

– Which practices were changed based on S. ?

– Were the data used to decrease the endemic rate ?

– Were the data used to assess the efficacy of interventions ?

– Are administrative & clinical staff aware of Surveillance Findings ?