Hypothesis-Generating Interviews

Goals 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: 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? Basic demographic information Clinical details Activities Food consumption

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? Standardized forms Types of questions Closed-ended Open-ended

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

References 1. Reingold, A. Outbreak investigations—a perspective. Emerg Infect Dis. Jan-Mar 1998;4: 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: CDC Epidemiology Program Office. Case studies in applied epidemiology. No An epidemic of Thyrotoxicosis. Available at:

References 4. 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): Available from 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 file/Epi_Course.pdf.

References 6. Schlech WF, Lavigne PM, Bortolussi RA, et al. Epidemic listeriosis—evidence for transmission by food. N Engl J Med. 1983;308: Fleming DW, Cochi SL, MacDonald KL, et al. Pasteurized milk as a vehicle of infection in an outbreak of listeriosis. N Engl J Med. 1985;312: