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3/29/2011 1
Critically reading epidemiologic studies
Principles of Epidemiology for Public Health (EPID600)
Victor J. Schoenbach, PhD home page
Department of EpidemiologyGillings School of Global Public Health
University of North Carolina at Chapel Hill
www.unc.edu/epid600/
Critically reading epidemiologic studies
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Outline
Reading and writing
Objectives, focus
Epidemiologic literacy
Steps in reading
Organization of a journal article
Application to an epidemiologic study
Critically reading epidemiologic studies
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Reading and writing
Various guides and books on critically reading epidemiologic studies
Aschengrau & Seage chapter is good
Better reader better writer
Critically reading epidemiologic studies
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Objectives, focus
Read/critique according to your objectives• Quick assessment of a reference• Systematic review of literature• Deep reading of an important article• Dissecting a study (e.g., exam article)
A full evaluation requires considerable subject matter knowledge.
Critically reading epidemiologic studies
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Epidemiologic literacy
The expectation for this course
1. Understand concepts, methods, and basic knowledge we’ve covered
2. Ability to extend that through reading
3. Reason and apply logic about concepts, methods, and basic knowledge
4. Differentiate based on importance
Critically reading epidemiologic studies
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Steps in reading
Expect to read article more than once (quickly, slowly, on exercise bicycle)
Read for big picture, read for details
Look up references
Try calculations
Be prepared for irregularities
Obtain consultation (except for an exam)
Critically reading epidemiologic studies
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Organization of a journal articleAbstract – all that most people will see
Introduction – why read this article
Methods – what was done
Results – what was found
Discussion – what it means
References – the foundation for the study
Tables and figures – ideally stand on own
Critically reading epidemiologic studies
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Application to an epidemiologic study
Study objective:• Describe and measure? • Examine associations?• Test hypotheses?
Rationale is central
Critique is keyed to these elements
Critically reading epidemiologic studies
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Questions for final paper critique - 1
1. Research objective and study rationale
2. Study design and study population
3. Key variables, measures, and data collection modes
4. Study conduct and quality control
5. Data analysis
Critically reading epidemiologic studies
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Questions for final paper critique - 2
6. Findings
7. Potential concerns
8. Linkage with previous knowledge
9. Conclusions, implications, recommendations
10.Overview of strengths and weaknesses
Critically reading epidemiologic studies
Grading guidelines• Graders will consider accuracy, understanding of
epidemiologic concepts relevant to the article, appropriate use of epidemiologic terminology, and evidence of critical thinking and judgment.
• Since epidemiologists can (and do) disagree, various answers may be acceptable if well articulated and supported.
• For each question, up to 20% of the points (i.e., 2 out of 10) may be awarded for quality of expression (logical sequence, clarity, succinctness, diction and usage, sentence structure, grammar and spelling, careful proofing, and adherence to instructions).
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Scoring – social comparison scale• Very poor / Seriously deficient – reflects very little
learning (5-24%: 1-2 out of 10 points)
• Poor / Unacceptable – disappointing (25-44%: 3-4 out of 10 points)
• Fair / Acceptable – acceptable, but prefer not to be judged by this answer (45-64%: 5-6 out of 10 points)
• Good / Very Good – shows proficiency in epidemiologic literacy (65-84%: 7-8 out of 10 points)
• Excellent / Outstanding – a candidate for advertising the course (85-100%: 9-10 out of 10 points)
3/29/2011 12Critically reading epidemiologic studies
Mechanics
• Write well-constructed paragraph(s), with complete, grammatically correct sentences, in logical sequence, appropriate transitions and good diction
• Use an outline for your answer but not as your answer
• Proof carefully (read aloud to yourself); use a spellchecker!
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1. Research objective, study rationale• What is the primary research objective?
• What is the rationale for this objective?
• How strong and well presented (e.g., conceptual framework, supporting evidence, logic) is the rationale in terms of:
• public health importance
• contribution to knowledge
• How well-grounded is the rationale in the published literature (biological, epidemiological)?
3/29/2011 14Critically reading epidemiologic studies
2. Study design and study population• Identify important design features
• Compared to other choices, what are the advantages and disadvantages for the specific objective(s) of this study?
• What is the study population?
• What are major eligibility criteria?
• How suited is study population, including eligibility criteria, for the objectives?
3/29/2011 15Critically reading epidemiologic studies
3. Key variables, measures, and data collection modes
• What are the key variables and their roles? • How are the variables defined & measured?• What are the major modes by which data
were collected?• How suited are the variables, their
definitions, their measurement methods, and the data collection modes for the objectives and rationale of this study?
3/29/2011 16Critically reading epidemiologic studies
4. . Study conduct and quality control
• How has study population been recruited?
• What steps to minimize non-participation and selective factors in recruitment and retention?
• How successful, overall, was the data collection?
• What steps were taken to improve and document accuracy of data collected?
3/29/2011 17Critically reading epidemiologic studies
5. Data analysis• Primary data analysis strategies used?• How are the primary variables coded?• Primary statistical parameters estimated?• How well suited is the choice of these
parameters?• How many participants in the primary
analyses?• How well do the authors deal with issues of
multicausation?
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6. Findings• What are the main findings?• Which are most important? • How well have the authors presented
them?• Should additional results or analyses
been reported or data shown?• Are extraneous results presented?
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7. Potential concerns• Accounting for all prospective members of
the study population• Does study population reflect the target
population well?• Major threats to validity important for
interpreting the findings?• How well did the authors discuss these
threats to validity?
3/29/2011 20Critically reading epidemiologic studies
8. Linkage with previous knowledge• Comparisons to findings from other relevant
studies and discussion of reasons for differences?
• Evaluate the evidence concerning the study objective, possible biological mechanisms and other criteria for causal inference
• How relevant and responsive to the study rationale was this discussion?
• In what ways, if any, have the authors advanced previous knowledge?
3/29/2011 21Critically reading epidemiologic studies
9. Conclusions, implications, recommendations
• What are the primary conclusions? Clear? • How well supported by findings &
discussion?• How directly do they relate to the objective
and rationale?• How well did authors address implications
and/or give insightful recommendations for next steps.
3/29/2011 22Critically reading epidemiologic studies
10. Strengths and weaknesses
• Key strengths in regard to study objective(s)?
• Take advantage of new methodology?
• Do these advance the field? How?
• Key limitations in regard to objective(s)?
• Are limitations shared by other studies?
• What would be needed to overcome limitations?
3/29/2011 Critically reading epidemiologic studies 23
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