Epidemiology Tools and Methods

2. Epidemiology Tools and Methods Session 2, Part 1

3. Learning ObjectivesSession 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

4. OverviewSession 2, Part 1 • Epidemiologic methods and resources • Public health laboratories • Data and technology • Examples of tools in action

5. Epidemiology Methods

6. Epidemiologic Methods • Person, place and time • Exposure assessment • Investigative field work and epidemiologic studies • Data analysis techniques

7. Referencesand Resources • Scientific literature • Control of Communicable Diseases Manual and other references • State-specific manuals and epidemiology websites • CDC website, references, experts

8. Public Health Laboratories

9. What Do Public Health Laboratories Do? • Disease prevention, control, and surveillance • Integrated data management • Reference and specialized testing • Environmental health and protection • Food safety • Laboratory improvement and regulation • Policy development • Emergency preparedness and response • Public health research • Training and education • Partnerships and communication

10. 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

11. 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

12. Data and Technology “Tools”

13. Sources of Data • Surveillance systems • Questionnaires, surveys, interviews • Medical and health facility records

14. 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.”

15. Surveillance Information, Dissemination, and Reporting Standardized data collection • Physicians • 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 Dissemination to those who need to know Change in public health practice (vaccination, reduction of risk factors, medical intervention, etc.) Public health planning and intervention • Public health officials • Health directors • Health policy officials • The public

16. Surveillance Data as a Tool • Establish baseline rate of disease • Detect epidemics • Estimate magnitude of a health problem • Determine geographic distribution • Facilitate planning

17. Surveillance Data Graphs Incidence rates of reported hepatitis A infections in Colorado and the United States, 2000-2009

18. 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

19. Outbreak investigations Questionnaire and Interview Data Rapid needs assessments

20. Questionnaires and Interviews:Other applications 1. Contact tracing Case-Patients Contact’s Contact High Risk Contact • 2. Case follow up

21. Data Management and Analysis • Computer software packages • Epi Info™ • SAS® • SPSS® • Stata®

22. Epi Info Softwarehttp://wwwn.cdc.gov/epiinfo/ • Features: • Relational database structure • On screen data entry form • Data analysis • Data graphing • Data mapping

23. 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

24. 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

25. Example Tuberculosis

26. 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

27. 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?

28. 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

29. 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

30. Tools Used

31. 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

32. 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.