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Discuss the uses of hypothesis-generating interviews
Present information on case-patient selection, questions to ask and when and where to conduct hypothesis-generating interviews.
Provide useful tips on how to conduct an interview during an outbreak.
Why use hypothesis-generating interviews?
To obtain initial clues on possible sources of exposure
To develop a hypotheses-testing questionnaire
To identify signs and symptoms of the disease
Why use hypothesis-generating interviews?
To help develop or refine the case definition
To develop a develop a demographic profile and identify the population at risk
To develop a list of potential exposures
Who Do We Interview? Case-patients
8 to 10 Differing demographic profiles Typical clinical presentation Occurring in the middle of the outbreak
Family member or friend if case-patient is unavailable
Parent or guardian if case-patient is a child
Health care providers, lab workers, clinical staff
Who Do We Interview? Examples:
1984-1985 Minnesota outbreak of Thyrotoxicosis
1997 Michigan and Virginia Salmonella outbreaks
What Do We Ask? Use existing hypothesis-
generating resources as a template and guide However, each outbreak is unique
and questions should meet the needs of the investigation at hand
Contact others who have investigated similar outbreaks Adapt the questionnaires used to the
particular setting
What Do We Ask? Known or suspected agent
Likely exposures Known reservoirs Modes of transmission Activities occurring during a specific period
based on known incubation period and date of onset
Unknown agent Broad, less specific questions Activities, clinical signs and symptoms
When And Where Do We Conduct The Interview
Early in the investigation Case-patients’ homes or health care
setting Other settings
e.g. the local health department, if several case-patients need to be brought together
Unusual approaches may be required 1981 epidemic of listeriosis in Canada 1983 epidemic of listeriosis in Massachusetts
How Do We Conduct The Interview? Face to face
Telephone (under special circumstances)
Language considerations Age, level of education, and other
case-patient characteristics Culturally sensitive wording Mindful of uncomfortable topic areas Avoid jargon and abbreviations
How Do We Conduct The Interview?
Tips: Review the literature Obtain background information Enhance interviewing and people
skills Act friendly and professional Use memory aids
How Do We Conduct The Interview? Tips:
Introduce yourself and give your credentials Explain the purpose of the interview and tell
the case-patient how long the interview will take
Be systematic but flexible when questioning Provide contact information Thank the interviewee for participating Acknowledge his or her contribution to the
investigation
Conclusions Hypothesis-generating interviews increase
efficiency of outbreak investigations by helping confirm the existence of an outbreak providing insights on potential causative agents identifying potential sources of exposure and
modes of transmission From the information obtained, investigators
create case definitions construct epi-curves proceed to test hypotheses through analytic
studies
References1. Reingold, A. Outbreak investigations—a
perspective. Emerg Infect Dis. Jan-Mar 1998;4:21-27.
2. Cummings SR, Stewart AL, Hulley SB. Designing questionnaires and data collection instruments. In Hulley SB, Cummings SR, Browner WS et al, eds. Designing clinical research. 2nd ed. Philadelphia, PA: Lippincott Williams and Wilkins; 2001:231-245.
3. CDC Epidemiology Program Office. Case
studies in applied epidemiology. No 873-703. An epidemic of Thyrotoxicosis. Available at: http://www.cdc.gov/eis/casestudies/Xthyrotox.instruct.873-703.pdf.
References4. Breuer T, Benkel DH, Shapiro RL, et al. A
multistate outbreak of Escherichia coli O157:H7 infections linked to alfalfa sprouts grown from contaminated seeds. Emerg Infect Dis. 2001;7(6):977-982. Available from http://wwwcdc.gov/ncidod/eid/vol7no6/breuer.htm.
5. US Department of Health and Human Services. Principles of epidemiology. An introduction to applied epidemiology and biostatistics. 2nd ed. Self-study course 3030-G. Lesson 6: Investigating an outbreak. Available at http://www.phppo.cdc.gov/PHTN/catalog/pdf-file/Epi_Course.pdf.