Transcript march7UGSurveil.ppt

Surveillance
Dr Amna Rehana Sidiqui
Assistant Professor
Department of Family and Community Medicine
Learning Objectives:
After studying this lesson you will be able to:
• Define public health surveillance and its main
components
• List the elements and uses of surveillance
• Describe sources for data that can be used for
public health surveillance
• Describe the flow of information for reportable
diseases
Public Health Surveillance
“Ongoing
systematic collection,
analysis, and interpretation of
outcome-specific data for use in
the planning, implementation,
and evaluation of public health
practice.”
Definition by Centers for Disease Control (CDC) USA
Surveillance is
Information for Action
Reported TB Cases* United States, 1982–2006
No. of Cases
28,000
26,000
24,000
22,000
20,000
18,000
16,000
14,000
12,000
10,000
1982
1986
1990
1994
Year
*Updated as of April 6, 2007.
1998
2002
2006
The components of surveillance and
resulting public health action
Elements of surveillance system
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Cases and deaths due to a given disease.
Laboratory results.
Prevention and control measures.
Environment.
Vector.
Reservoir.
Population
Fig. 2
Cholera:
Reported
cases &
Case fatality
Rates (CFR),
by Continent
By
CFR= # of TB cases dying in that yr / # of TB cases identified in that yr
Conceptual Taxonomy
Public Health Surveillance
Medical Utilization
and Adverse Events
Drug
Vaccine
Disease
Other
Products/Services
Traditional
Infectious Disease
Birth defect
‘Syndromic’
Other
Injuries
Etc.
Purposes of Public Health Surveillance
• Assess public health status about a factor/s
• Setting public health priorities; e.g. polio first…
• Evaluate prevention and control programs
• Generating hypothesis & Stimulating research; e.g.
relationship of TB and HIV
Uses of Public Health Surveillance
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Estimate magnitude of the problem
Guide immediate action for cases
Determine geographic distribution of illness
Portray the natural history of a disease
Detect epidemics/define a problem
Generate hypotheses, stimulate research
Monitor changes in infectious agents
Detect changes in health practices
Facilitate planning
Evaluate control measures
Policy Changes e.g. Measles vaccine booster
TB Case Rates,* United States, 2006
D.C.
< 3.5 (year 2000 target)
3.6–4.6
> 4.6 (national average)
*Cases per 100,000.
Evaluate control measures of MEASLES
MEASLES — by year, United
States, 1983–1998
450
Reported Cases Thousands)
Reported Cases (Thousands)
United States, 1963-1998
Vaccine
500
licensed
400
350
300
250
200
150
30
25
20
15
10
100
5
0
1983
1988
1993
1998
Year
50
0
1963
1968
1973
1978
1983
Year
1988
1993
1998
Data Sources for Surveillance
• Notifiable diseases (Reporting is mandatory, legal, &
reportable diseases vary by region)
• Laboratory specimens (Salmonella—serotypes,
Blood Lead Measurements, HIV)
• Vital records (Infant Mortality Surveillance, Birth &
Death Certificates)
• Sentinel surveillance (selected sites ; work-related
Asthma, lead poisoning,…)
• Registries (Cancer& congenital defects)
• Surveys (Nutrition Examination Survey,….)
• Other data sources (Vaccine Adverse Event
Reporting, drug reaction,…)
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Types of Surveillance
Passive surveillance
health-care providers send reports to a health department on
the basis of a known set of rules and regulations, is called
passive surveillance.
• Inexpensive, provider-initiated
• Good for monitoring large numbers of typical health events
• Under-reporting is a problem
Active surveillance
▫ active surveillance (health department- initiated) health
department approach health providers ; is usually limited
to specific diseases over a limited period of time, such as
after a community exposure or during an outbreak.
Attributes of a surveillance system
--- Simplicity – time spent in maintaining
--- Flexibility – can adapt to changes
--- Data quality - validity
--- Acceptability – by stakeholders
--- Sensitivity-can detect …
--- Representativeness
--- Timeliness – detected and reported
--- Stability - continues without breaks
Data collection
1. Routine reporting system
Hospitals, health centers, health facilities, CHW.
Advantages:
Inexpensive and efficient.
Standardized.,
Disadvantages:
Incomplete
Busy doctors & nurses
New and complex disease entities
must also be monitored…
• New syndromes may emerge that present in an
atypical manner
• Syndromic surveillance uses health-related data
that precede diagnosis and signal a sufficient
probability of a case or an outbreak to warrant
further public health response
Example of Passive Surveillance
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Day 1- feels fine
Day 2- headaches, fever - buys Tylenol
Day 3- develops cough - calls nurse hotline
Day 4- Sees private doctor – dx with “flu”
Day 5- Worsens - calls ambulance seen in ED
Day 6- Admitted - “pneumonia”
Day 7- Critically ill - ICU
Day 8- Expires - “respiratory failure”
Case enters surveillance system through
hospital reporting
Example of Syndromic Surveillance
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Day 1- feels fine
Pharmaceutical Sales
Day 2- headaches, fever - buys Tylenol
Nurse’s Hotline
Day 3- develops cough - calls
nurse hotline
Manageddoctor
Care Org
Absenteeism records
Day 4- Sees private
- dx “flu”
Day 5- Worsens - callsAmbulance
ambulance
- seen in ED
Dispatch (EMS)
Day 6- Admitted - “pneumonia”
ED Logs
Day 7- Critically ill - ICU
Day 8- Expires - “respiratory failure”
Case is under immediate investigation by the
LHD because of the pre-diagnostic information
gathered
2-Sentinel reporting system
Selected health units; e.g. influenza in USA to
develop vaccine for that year after typing for
circulating strain for that year
Advantages:
More consistent pictures.
Motivated.
Disadvantages:
Not representative
Changes with served population
e.g. use of the same influenza vaccine in other countries
which was identified for USA population
3-Surveys and special studies
e.g. The National Health and Nutrition Examination Survey
(NHANES) program of studies designed to assess the health and
nutritional status of adults and children in the United States.
Advantages
Broad estimate.
Measure reliability.
Relieve health care workers.
Disadvantages:
Large sample size.
Expensive
4-Case and outbreak investigations
e.g. HIV cases when first identified
On occasion.
Used as a next step e.g. to plan intervention
Post outbreak surveillance (e.g. to confirm that outbreak is over)
Early warning systems: e.g. surveillance for risk factors in
malnourished children who may be vulnerable and will acquire
diseases before it spreads in healthy children
Data collection procedures
• Operational definition
• Instruments
• Registers
• Questionnaires
• Case investigation form
• Pre-test the instrument
• Source; Laboratory; hospitals…
Data collection
• Training
• Supervision
• Quality control
• Reporting; frequency for
monitoring and interpretation
Analyze and interpret data
• Summary tables.
• Disease charts.
• Maps.
• Rates & ratios
• More analysis for pattern and
causes
Steps in Surveillance data Analysis
• Data quality
• Descriptive analysis
▫ Time
▫ Place
▫ Persons
• Generate hypothesis
• Test hypothesis
Data Quality Issues
• Missing values
• Attraction to round figures
• Data entry errors
• Bias related to lack of representativity
▫ Cases more severe
▫ Urban > rural
▫ Source not represented
(private sector, GPs)
Data Quality
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completeness and validity of the data
percentage of "unknown" or "blank
Case definition
Training of team
Manuals
Active versus passive
Burden of diseases
• Reporting only confirmed cases may not reflect
true status resulting in ineffective control as an
iceberg situation may exist with clinical and
subclinical cases
• Only severe cases are reported
• Under reporting may lead to high case fatality
rates; resource utilization affected
Timeliness of disease notification
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Health event occurs
Identified by health care system
Reported to local health authority
Verification/investigation by PHS
Health event reported to other systems
Analyses of health data
Dissemination of surveillance finding
Actions based on surveillance findings
Early warning system
• Major threats to the population; 0-4 & 5 or more
years of age, have been identified.
• Severe malnutrition, injuries, acute watery
diarrhoea, bloody diarrhoea, acute flaccid paralysis,
acute respiratory infections, neonatal tetanus,
malaria, suspected measles, suspected meningitis,
acute jaundice syndrome and acute FUO
• A threshold for each is defined; unusual pattern or
occurrence will triggers investigations and
responses.
33
Dr. Salwa Tayel
8/5/1430
Prepare and present reports
• Review objectives.
• Review tables, graphs & maps.
• Add short narrative to explain findings
COMPARING TO PREVIOUS REPORTS.
• Describe action plan.
• Disseminate the report
34
Dr. Salwa Tayel
8/5/1430
EXERCISE
Surveillance system in Hospital
• High risk of hospital acquired infections (HAI)
that leads to high mortality, longer length of
stay, and huge costs of hospitalization
• First Surveillance and then research
• How much mortality, cost, length of stay could
be averted by reducing HAI?
• How will you start?
• Person, place and time ?
Needs and Steps
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Assess your resources
Step wise fashion or all at once?
Training of individuals
Pilot testing
Obtaining data, case definitions, standards
Monitoring/continuous / frequency ? 3 months
Interpretation ; comparing rates by quarters
Analyses ; developing research hypothesis
Dissemination ; publication
Descriptive epidemiology
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What are the infection rates in ….
What is the mortality rate in ….
What is the usual length of stay …
What are the important organisms that are
reported from …..
Any previous data?
Any previous outbreak data?
Numerator?
Denominator?
Setting/s defined
Numerators
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Case definitions required
Sepsis, Pneumonias, UTI, SWI etc.
Who will diagnose ? (for stability of rates)
Standard definitions / CDC
Laboratory based surveillance
Active surveillance
Hospital Acquired Infections in High Risk Area (Mixed type ICU)
April 1998 – March 2001
30
Rate / 1000 Device DAys
25
20
15
10
5
0
-5
AprJun'98
JySep'9
8
OctDec'9
8
JanMar'9
9
AprJun'99
JulSep'9
9
OctDec'9
9
JanMar'0
0
AprJn00
JySep'0
0
JanM01
BSI
26
27
23.5
22.72
24.76
15.9
21.27
13.88
18.7
18.6
8.6
5.1
Pneumonia
2.5
5.2
7.4
7.08
4.21
6.2
2.6
1.21
9.2
8.5
10.6
10.3
UTI
1.2
0
2.42
3.38
0
0
1.97
2
2.6
0.8
0
6.5
BSI=Blood Stream Infections; UTI=Urinary Tract Infections
Reference
50th Percentile
40
Summary
• Surveillance for ………
▫ Case definition
▫ Sources of data
▫ Analysis
▫ Interpretation
▫ Dissemination - REPORTING
• Actions