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
Retrospective
• Depends on completeness, validity & accuracy of existing data. • Does not identify problems as promptly as concurrent does. • But isn’t expensive.
Surveillance methods-2 • Active : •Passive :
• accurate • complete • expensive • • • • 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. 2. 3. 4. 5. 6. 7. Daily reports of microbiology labs. Medical records of febrile patients. Medical records of patients taking antibiotics. Medical records of isolated patients Daily interview with nurses & patients Periodic review of autopsy reports 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 ?