Transcript STROBE Statement - The EQUATOR Network

STROBE Statement
STrengthening the Reporting of
OBservational Studies in Epidemiology
Iveta Simera
The EQUATOR Network
Centre for Statistics in Medicine, Oxford, UK
April 2012
Observational studies
Many types of studies - right research design
depends on the question we ask
Observational studies
• Large proportion of research
• Can be valuable (e.g. AE) but also many
disadvantages (confounding, bias)
Without comparison group – descriptive:
(do not try to qualify the relationships but give us a
perspective of what is happening in the population,
prevalence or experience of a group)
•
Case reports, case series, qualitative
studies, some cross-sectional studies
(surveys)
With comparison group - analytical
(attempts to qualify relationship between two factors
– effect of an intervention / exposure on an outcome)
•
Cohort studies, case-control studies, some
cross-sectional studies
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Difference in analytical designs
Experimental studies:
•
Researcher
manipulates exposure
by allocating
participants to
Intervention (Exposure)
group
Observational studies with
a comparison group:
•
Researcher simply
measures the exposure or
treatments of the groups
•
These studies all include
matched groups of
participants
•
They assess associations
between exposures and
outcomes
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Cohort studies
• Cohort = group of Roman soldiers
• Start with exposure (variable) then follow for
outcome
• Data are obtained from groups who have been
exposed or not exposed to the factor of
interest
• Best for study the effect of predictive risk
factors on an outcome
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Case-control studies
• Patients with a certain outcome or disease
and an appropriate group of controls without
the outcome or disease are selected
(usually with careful consideration of
choice of controls, matching)
• Information is obtained on whether the
participants have been exposed to the factor
under investigation
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Cross-sectional studies
• Examine the relationship between diseases
(or other health-related characteristics) and
other variable of interest as they exist in a
defined population at one particular time
(outcomes and exposures are both
measured at the same time)
• Best for quantifying the prevalence of a
disease or risk factor, and for quantifying the
accuracy of a diagnostic test
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STROBE
Grimes, DA, Schulz KF. An overview of clinical research:
the lay of the land. Lancet 2002; 359; 57-61.
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STROBE Statement
• Guidance on how to report observational studies well
(which is rare!)
– Focus on 3 main study designs: cohort, case-control,
cross-sectional studies
• Published in Oct 2007: short paper and E&E
• Adopted by many journals
Find it on:
www.equator-network.org
www.strobe-statement.org
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Three STROBE extensions (1)
• STREGA (2009)
– reporting of genetic association studies
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Three STROBE extensions (2)
• STROBE – ME (Oct 2011)
– Reporting molecular epidemiology (biomarker
studies)
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Three STROBE extensions (3)
• STROBE abstract
- Reporting observational
studies in conference
abstracts (online draft)
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STROBE
• Checklist with 22 items
– Heading (where in paper), item No
– Recommendation, divided into:
cohort, case-control, cross-sectional study - where different
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Title and abstract:
1.a) Indicate the study’s design with a commonly used term
in the title or the abstract
b) Provide in the abstract an informative and balanced
summary of what was done and what was found
Introduction
Background/Rationale
2.Explain the scientific background and rationale for the
investigation being reported
Objectives
3. State specific objectives, including any prespecified
hypothesis
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Methods:
Study Design
4. Present key elements of study design early in the
paper
(what design, what was compared, which controls and
why...etc)
Setting
5.
Describe the setting, locations, and relevant dates,
including periods of recruitment, exposure, follow-up,
and data collection
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Methods - continued
Participants
6.a) Cohort study:
• eligibility criteria
• sources and methods of participant selection
• follow-up methods
Case-control study:
• eligibility criteria
• sources and methods of case ascertainment and control
selection
• rationale for the choices of cases and controls
Cross-sectional study:
• eligibility criteria
• sources and methods of participant selection
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Methods - continued
Participants
6.b) Cohort study:
For matched studies, give matching criteria and number of
exposed and unexposed
Case-control:
For matched studies, give matching criteria and the number of
controls per case
Variables
7. Clearly define all outcomes, exposures, predictors,
potential confounders, and effect modifiers. Give
diagnostic criteria, if applicable
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Methods - continued
Data sources/measurement
8. For each variable of interest, give sources of data and
details of methods of assessment (measurement)
Describe comparability of assessment methods if
there is more than one group
* Give information separately for cases and controls in
case-control studies and, if applicable, for exposed
and unexposed in cohort and cross-sectional studies
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Methods - continued
Bias
9. Describe any efforts to address potential sources of
bias
(ie systematic deviation of a result from the true value)
e.g.: recall bias, detection bias,
interviewer bias, selection bias
Very important
in observational
studies!
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Methods - continued
Study size
10. Explain how the study size was arrived at
(should be large enough to arrive at a point estimate
with a reasonably narrow confidence interval)
Quantitative variables
11. Explain how quantitative variables were handled in the
analyses. If applicable, describe which groupings
were chosen and why
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Methods - continued
Statistical methods
12.a) Describe all statistical methods, including those
used to control confounding
(≠bias, confounding: association true but caused
by something else)
b) Describe any methods used to examine subgroups
and interactions
c) Explain how missing data were addressed
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Methods - continued
Statistical methods - continued
12.d) Cohort study:
If applicable, explain how loss to follow-up was addressed
Case-control:
If applicable, explain how matching of cases and controls
was addressed
Cross-sectional:
If applicable, describe analytical methods including
sampling strategy
e) Describe any sensitivity analyses
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Results
Participants
13. a) Report numbers of individuals at each stage of study
- e.g., numbers potentially eligible, examined for
eligibility, confirmed eligible, included in the study,
completing follow-up, and analysed
b) Give reasons for non-participation at each stage
c) Consider use of a flow diagram
*
Give information separately for cases and controls in case-control
studies and, if applicable, for exposed and unexposed in cohort
and cross-sectional studies
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Results - continued
Descriptive data
14. a) Give characteristics of study participants
(e.g. demographic, clinical, social) and information on
exposures and potential confounders
b) Indicate number of participants with missing data for
each variable of interest
c) Cohort study:
Summarise follow up time (e.g. average and total
amount)
*
Give information separately for cases and controls in case-control
studies and, if applicable, for exposed and unexposed in cohort and
cross-sectional studies
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Results - continued
Outcome data
15. Cohort study:
Report numbers of outcome events or
summary measures over time
Case-control:
Report numbers in each exposure category, or summary
measures of exposure
Cross-sectional:
Report number of outcome events or summary
measures
*
Give information separately for cases and controls in case-control
studies and, if applicable, for exposed and unexposed in cohort and
cross-sectional studies
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Results - continued
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Main results
a) Give unadjusted estimates and, if applicable,
confounder-adjusted estimates and their precision
(e.g. 95%CI). Make clear which confounders were
adjusted for and why they were included
b) Report category boundaries when continuous
variables were categorised
c) If relevant, consider translating estimates of
relative risk into absolute risk for a meaningful time
period
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Results - continued
Other analyses
17. Report other analyses done, e.g. analyses of subgroups
and interactions, and sensitivity analyses
Discussion
Key results
18. Summarize key results with reference to study objectives
Limitations
19. Discuss limitations of the study, taking into account
sources of potential bias or imprecision. Discuss both
direction and magnitude of any potential bias
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Discussion - continued
Interpretation
20. Give a cautious overall interpretation of
results considering objectives, limitations,
multiplicity of analyses, results from similar
studies, and other relevant evidence
Generalisability
21. Discuss the generalisability (external validity) of the
study results
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Other information
Funding
22.
Give the source of funding and the role of the
funders for the present study and, if applicable, for
the original study on which the present article is
based
More detailed explanation:
Vandenbroucke JP, von Elm E, Altman DA, et al. Strengthening the Reporting of
Observational Studies in Epidemiology (STROBE): Explanation and
Elaboration. PLoS Med 4(10): e297.doi:10.1371/journal.pmed.0040297
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www.equator-network.org
www.strobe-statement.org
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