Transcript Document

Session 2, Part 1
Epidemiology Tools and Methods
Learning Objectives
Session 2, Part 1
• List methods that can be used for
epidemiologic assessment of a health
problem
• Identify ways that public health
laboratories carry out epidemiologic
functions
• Identify ways that data can be collected
during an epidemiologic investigation
Overview
Session 2, Part 1
• Epidemiologic methods and resources
• Public health laboratories
• Data and technology
• Examples of tools in action
Epidemiology Methods
Epidemiologic Methods
• Person, place and time
• Exposure assessment
• Investigative field work and epidemiologic
studies
• Data analysis techniques
References and Resources
• Scientific literature
• Control of Communicable
Diseases Manual and other
references
• State-specific manuals and
epidemiology websites
• CDC website, references,
experts
Public Health Laboratories
What Do Public Health
Laboratories Do?
1. Disease prevention, control, and surveillance
2. Integrated data management
3. Reference and specialized testing
4. Environmental health and protection
5. Food safety
6. Laboratory improvement and regulation
7. Policy development
8. Emergency preparedness and response
9. Public health research
10. Training and education
11. Partnerships and communication
Laboratory Surveillance,
Monitoring, Reporting
• Surveillance
– Vector borne diseases
– Communicable diseases
– Food borne and waterborne diseases
• Monitoring
– Newborn screening and genetics
– Radiation monitoring and detection
– Food safety or other environmental issues
• Reporting
– Two-way with state health departments
Association of Public Health
Laboratories (APHL)
• Purpose
– Promote the role of public health laboratories
– Promote improvement in laboratory practice and
health outcomes
• Programs
– Environmental health
– Food safety
– Public health preparedness and response
• Working relationship with CDC, EPA, FBI, DHS
Data and Technology
“Tools”
Sources of Data
• Surveillance systems
• Questionnaires, surveys,
interviews
• Medical and health facility
records
Surveillance
“The ongoing systematic collection,
analysis, and interpretation of health data,
essential to the planning, implementation,
and evaluation of public health practice,
closely integrated with the timely
dissemination to those who need to know.”
Surveillance Information,
Dissemination, and Reporting
• Physicians
Standardized data collection
• Laboratories
• STD clinics
• Community
health clinics
County and state health
departments, CDC
analyze data using
statistical methods
Dissemination to those
who need to know
Public health
evaluation
Change in public
health practice
(vaccination, reduction
of risk factors, medical
intervention, etc.)
Dissemination
to those who
need to know
Public health planning
and intervention
• Public health officials
• Health directors
• Health policy officials
• The public
Surveillance Data as a Tool
• Establish baseline rate of
disease
• Detect epidemics
• Estimate magnitude of a
health problem
• Determine geographic
distribution
• Facilitate planning
Surveillance Data Graphs
Incidence rates of reported hepatitis A infections in Colorado
and the United States, 2000-2009
Surveillance Data Maps
North Carolina Salmonella Rates by County: 2002
Salmonella rate
Rate numerators: NC Communicable Disease Data for 2000
Rate denominators: U.S. Census population data, by county, for 2000
Questionnaire and Interview
Data
Outbreak
investigations
Rapid needs
assessments
Questionnaires and Interviews:
Other applications
1. Contact tracing
CasePatients
High Risk
Contact
2. Case follow up
Contact’s
Contact
Data Management and Analysis
• Computer software packages
– Epi Info™
– SAS®
– SPSS®
– Stata®
Epi Info Software
http://wwwn.cdc.gov/epiinfo/
• Features:
– Relational database structure
– On screen data entry form
– Data analysis
– Data graphing
– Data mapping
Epidemiologic Software
• Store databases
– Surveillance systems
– Outbreak investigations
– Medical records
• Generate descriptive statistics
– Frequencies, proportions, rates
– Graphs: bar, line, histogram (Epi Curves)
– Maps: census tracts; counties; districts
• Generate statistics
– Test statistics: t-test, chi-square
– Measures of association: Odds ratios, risk ratios
The Epidemiologist
• Generate hypotheses
– Make judgments about linkages
between exposure and outcome
• Interpret data
– Identify or correct mistakes
– Interpret statistical and laboratory
tests
• Make decisions
– Determine if an epidemic is in
progress
– Recommend control measures
Example
Tuberculosis
TB Exposure Investigation
Background
• Hospital nurse with active TB died
• Several unknowns:
–
–
–
–
Duration of infectiousness
Number of patients exposed
Number of hospital visitors exposed
Identity of hospital visitors
Data-Based Decisions
• Interviews
– Nurse family members
– Hospital patients and visitors
• Result
– Infectious period: July 2003-April 2004
– Need to screen 900 patients and 1500
visitors
• Further questions
– Does the time period for exposure need to
be expanded?
– Did exposed persons spread disease to
their own contacts?
– Were high-risk patients exposed?
– What are the TB reaction rates among
patients, contacts?
Investigation and Response
• Finding social and
professional contacts
– Coordinating three districts
– Hospital employee and staff
screening
• Screening and testing
patients and visitors
– Approximately 900 patients &
1500 visitors
• Requesting outside help
Outcomes
• 2500 people screened
– 2300 tuberculin skin tests
• 2100 (92%) read
– 128 positives
– More than 350 x-rays
• 120+ hours of clinic time
• New TB testing policy
and employee illness
monitoring at the hospital
Tools Used
To find and screen contacts: To interpret results:
• Computers
• Analytical tools
• Administrative capacity
• Communications
• Interview instruments
• Policy development for
infection control
• Reference journals and
institutions
• Laboratory
• Diplomacy
Summary
• Epidemiologists employ investigative and analytic
tools to collect data and assess factors that cause
disease
• Laboratories play a role in diagnosis and
surveillance for carrying out public health
investigations and core epidemiologic functions
• Statistical software is used for data management
and analysis
• Human effort is used to investigate, generate
hypotheses, and interpret results
References and Resources
•
Association of Public Health Laboratories [Web site]. Available at:
http://www.aphl.org. Accessed March 1, 2012.
•
Centers for Disease Control and Prevention [Web site]. Available at:
http://www.cdc.gov. Accessed March 1, 2012.
•
Smallpox Response Plan Guide (Version 3.0) [Web page]. Division of
Bioterrorism Preparedness and Response, Centers for Disease Control and
Prevention; June 23, 2004. Available at:
http://www.bt.cdc.gov/agent/smallpox/response-plan. Accessed March 1,
2012.
•
National Laboratory System {Web page]. Division of Laboratory Systems,
Centers for Disease Control and Prevention; July 12, 2004. Available at:
http://www.phppo.cdc.gov/mlp/nls.aspx. Accessed March 1, 2012.
•
Inhorn SL, Astles JR, Gradus S, et al. The State Public Health Laboratory
System. Public Health Rep. 2010; 125(Suppl 2):4-17. Available at:
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2846798/. Accessed March 1,
2012.