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 surveillance Sources 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 = N o. 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 ?