Statistics

Surveillance

Community
Lecture38

د.جواد

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DEFINITIONS OF SURVEILLANCE

“The continued watchfulness over the distribution and trends of incidence through the systematic collection, consolidation, and evaluation of morbidity and mortality reports and other relevant data, together with dissemination to those who need to know.”

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DEFINITIONS OF SURVEILLANCE

“Surveillance serves as the brain and nervous system for programs to prevent and control disease.”

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DEFINITIONS OF SURVEILLANCE

“Systematic ongoing collection, collation, and analysis of data and the timely dissemination of information to those who need to know so that the action can be taken”
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What Surveillance Is

Systematic, ongoing…
Collection
Analysis
Interpretation
Dissemination
…of health outcome data


Health action

investigation

control
prevention

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DEFINITIONS OF SURVEILLANCE

Collection of health data expressly for use in health planning, disease control/ prevention, and/or health promotion
Ongoing collection of data
Timely analysis
Easily understood
Dissemination of results
Action based on results
Periodic evaluation of the system
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USES OF SURVEILLANCE SYSTEMS (1)

To monitor changes or trends in health factors:
Prevalence/incidence of disease and/or
risk factors
Emerging diseases
Geographic distribution
Risk group distribution
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USES OF SURVEILLANCE SYSTEMS (2)

To detect outbreaks/early warning systems
Human disease
Zoonotic diseases
Food safety
Drug-resistant organisms (e.g., MDR-TB)

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USES OF SURVEILLANCE SYSTEMS (3)

To provide health information that can be used to design rational intervention programs
To evaluate the effectiveness of intervention strategies (e.g., vaccines, health education/behavioral programs, legislation)

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SURVEILLANCE VS. SCREENING

Surveillance
Data collection to measure magnitude, changes, and trends in populations
The objective is intervention in defined populations
Screening
Testing to identify individuals with infection or disease
Objective is either:
Personal intervention
Protection of the public (e.g., blood donors)
Measurement of prevalence in screened populations

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REQUIREMENTS FOR SURVEILLANCE
Diagnostic algorithm
Staff members
Sampling frame
Access/network
Competent laboratory

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SURVEILLANCE SYSTEMS

DEFINING A CASE

Establishing a functional case criteria

Quickly and easily defined
Selecting the right test or definition
Easy, specific
Clinical versus epidemiological diagnostic criteria
Function over precision
Disease versus infection
AIDS and HIV infection


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SURVEILLANCE SYSTEMS

ACTIVE VS. PASSIVE SURVEILLANCE

Passive = reporting

Hospitals
Laboratories
Clinics
Physicians
Active = searching

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SENTINEL SURVEILLANCE

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SURVEILLANCE SYSTEMS

SENTINEL GROUPS (HIV)


• Homosexual/bisexual
• Commercial sex workers
• Returning overseas workers
• Intravenous drug users
• Males at STD clinics
• Other groups
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EVALUATION OF A SURVEILLANCE SYSTEM

Sensitivity
Timeliness
Representativeness
Predictive value positive
Acceptability
Flexibility
Simplicity
Cost/benefit
Dissemination of results
Appropriate action taken


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BEHAVIORAL SURVEILLANCE

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Measure increasing/decreasing risk

Evaluate effectiveness of intervention efforts
OBJECTIVE
TO DETECT CHANGES IN RISK BEHAVIORS OF A POPULATION

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