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Questions and Answers
What does the STROBE statement help evaluate?
What does the STROBE statement help evaluate?
External validity refers to whether the results can be generalized beyond the study sample.
External validity refers to whether the results can be generalized beyond the study sample.
True (A)
What are the two main components that a checklist for critical assessment of observational studies should have?
What are the two main components that a checklist for critical assessment of observational studies should have?
Research question and study design
A prospective ______ design was used to study the effect of estrogen-progestin combination use on cardiovascular disease.
A prospective ______ design was used to study the effect of estrogen-progestin combination use on cardiovascular disease.
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Which of the following is NOT a key element when considering a study's research question?
Which of the following is NOT a key element when considering a study's research question?
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Match the components of a critical assessment checklist with their descriptions:
Match the components of a critical assessment checklist with their descriptions:
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The rationale for investigating the research question should always be found in the study's results section.
The rationale for investigating the research question should always be found in the study's results section.
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According to Grodstein F, Stampfer MJ, Manson JE, what medical condition were they studying?
According to Grodstein F, Stampfer MJ, Manson JE, what medical condition were they studying?
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What is a key reason observational studies are important in medical literature?
What is a key reason observational studies are important in medical literature?
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The results of observational studies should always be accepted without critical evaluation.
The results of observational studies should always be accepted without critical evaluation.
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What type of error occurs when there are systematic differences in how exposures and outcomes are measured between study groups?
What type of error occurs when there are systematic differences in how exposures and outcomes are measured between study groups?
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A ______ is a factor associated with both the outcome and the treatment but is not a consequence of the treatment.
A ______ is a factor associated with both the outcome and the treatment but is not a consequence of the treatment.
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Which of the following best describes selection bias?
Which of the following best describes selection bias?
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What is one way to address unobservable confounding factors in observational studies?
What is one way to address unobservable confounding factors in observational studies?
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Internal validity refers to whether the study results are generalizable to other populations.
Internal validity refers to whether the study results are generalizable to other populations.
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What are two approaches to control for observable confounding factors?
What are two approaches to control for observable confounding factors?
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The variable quality of observational studies can compromise their internal and ______ validity.
The variable quality of observational studies can compromise their internal and ______ validity.
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Match the following terms with their descriptions:
Match the following terms with their descriptions:
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What effect does progestin use have on cholesterol levels in relation to cardiovascular disease (CVD)?
What effect does progestin use have on cholesterol levels in relation to cardiovascular disease (CVD)?
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There is sufficient information on the effects of estrogen-progestin combination use on cardiovascular disease.
There is sufficient information on the effects of estrogen-progestin combination use on cardiovascular disease.
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What was the goal of the prospective cohort study design regarding hormone replacement therapy (HRT) and CVD?
What was the goal of the prospective cohort study design regarding hormone replacement therapy (HRT) and CVD?
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The study selected participants from a source population of ______, with a total sample size of ______ patients.
The study selected participants from a source population of ______, with a total sample size of ______ patients.
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What is a primary reason for evaluating inclusion/exclusion criteria in study populations?
What is a primary reason for evaluating inclusion/exclusion criteria in study populations?
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Comparison groups in studies should represent the same group of individuals as treatment groups.
Comparison groups in studies should represent the same group of individuals as treatment groups.
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What should be reported to help assess the comparability of groups in a study?
What should be reported to help assess the comparability of groups in a study?
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The cohort selected for the Nurses’ Health Study primarily consisted of nurses aged ___ to ___ years.
The cohort selected for the Nurses’ Health Study primarily consisted of nurses aged ___ to ___ years.
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Why might the results of the Nurses’ Health Study not be generalizable to the broader population?
Why might the results of the Nurses’ Health Study not be generalizable to the broader population?
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Attrition rates in a study do not need to be reported if they are unrelated to the outcome.
Attrition rates in a study do not need to be reported if they are unrelated to the outcome.
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What analysis method should always be utilized regarding the subjects in a study?
What analysis method should always be utilized regarding the subjects in a study?
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Match the following types of studies with their characteristics:
Match the following types of studies with their characteristics:
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What happens to cardiovascular disease (CVD) risk during the first year of hormone replacement therapy (HRT) use?
What happens to cardiovascular disease (CVD) risk during the first year of hormone replacement therapy (HRT) use?
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CVD risk is excluded for those who developed it after being initiated on HRT between surveys.
CVD risk is excluded for those who developed it after being initiated on HRT between surveys.
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What methods are commonly used to measure exposure in studies?
What methods are commonly used to measure exposure in studies?
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In case-control studies, a _____ look-back period may underestimate exposure for conditions that develop slowly.
In case-control studies, a _____ look-back period may underestimate exposure for conditions that develop slowly.
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Match the types of hormone replacement therapy (HRT) exposure to their definitions:
Match the types of hormone replacement therapy (HRT) exposure to their definitions:
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Which factor is crucial when determining the look-back period in case-control studies?
Which factor is crucial when determining the look-back period in case-control studies?
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Statistical analysis should not be appropriately adjusted for observed confounding factors in studies.
Statistical analysis should not be appropriately adjusted for observed confounding factors in studies.
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What stratifications were made for the current dose of estrogen to examine CVD risk?
What stratifications were made for the current dose of estrogen to examine CVD risk?
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Progestin use has been shown to have a beneficial effect on arterial dilation and blood flow.
Progestin use has been shown to have a beneficial effect on arterial dilation and blood flow.
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Which of the following is NOT a general observational study design?
Which of the following is NOT a general observational study design?
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A ______ cohort study design was used to investigate the relationship between hormone replacement therapy (HRT) and CVD.
A ______ cohort study design was used to investigate the relationship between hormone replacement therapy (HRT) and CVD.
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What was the primary goal of the prospective cohort study mentioned in the text?
What was the primary goal of the prospective cohort study mentioned in the text?
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Match the following observational study designs with their characteristics:
Match the following observational study designs with their characteristics:
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What is a potential benefit of using a prospective cohort study design, especially when studying rare outcomes?
What is a potential benefit of using a prospective cohort study design, especially when studying rare outcomes?
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The study on HRT and CVD had a limited number of patients and a short follow-up period.
The study on HRT and CVD had a limited number of patients and a short follow-up period.
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What is a key consideration when evaluating the appropriateness of the source population for a study?
What is a key consideration when evaluating the appropriateness of the source population for a study?
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What percentage reduction in risk for major coronary artery disease is indicated by the age-adjusted RR of 0.45 in postmenopausal women using estrogen?
What percentage reduction in risk for major coronary artery disease is indicated by the age-adjusted RR of 0.45 in postmenopausal women using estrogen?
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The unadjusted rates of major coronary artery disease for the study group were higher than those for the control group.
The unadjusted rates of major coronary artery disease for the study group were higher than those for the control group.
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What is the number needed to treat (NNT) according to the provided calculations?
What is the number needed to treat (NNT) according to the provided calculations?
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Caution should be taken with the use of HRT for primary prevention of ________.
Caution should be taken with the use of HRT for primary prevention of ________.
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Match the following terms with their corresponding descriptions:
Match the following terms with their corresponding descriptions:
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What is a significant reason for the black-box warnings issued by the FDA?
What is a significant reason for the black-box warnings issued by the FDA?
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It is recommended that practice implications should be based solely on one study’s findings.
It is recommended that practice implications should be based solely on one study’s findings.
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What did the authors conclude about the addition of progestin to estrogen regarding cardioprotective effects?
What did the authors conclude about the addition of progestin to estrogen regarding cardioprotective effects?
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Flashcards
STROBE Statement
STROBE Statement
A set of guidelines that helps evaluate the quality of observational studies in epidemiology.
External Validity
External Validity
The extent to which the results of a study can be generalized to other populations and settings.
Research Question
Research Question
A well-defined question that guides the research, including any specific predictions.
Study Design
Study Design
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Study Population
Study Population
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Exposure
Exposure
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Outcome
Outcome
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Data Analysis and Confounding
Data Analysis and Confounding
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Bias in observational studies
Bias in observational studies
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Selection bias
Selection bias
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Measurement bias
Measurement bias
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Confounding factor
Confounding factor
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Stratification
Stratification
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Statistical adjustment
Statistical adjustment
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Instrumental variable methods
Instrumental variable methods
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Heckman selection model
Heckman selection model
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Cohort Study
Cohort Study
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Case-Control Study
Case-Control Study
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Source Population
Source Population
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Target Population
Target Population
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Inclusion Criteria
Inclusion Criteria
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Exclusion Criteria
Exclusion Criteria
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Cross-Sectional Study
Cross-Sectional Study
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Case-Series Study or Case Report
Case-Series Study or Case Report
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Subject Selection
Subject Selection
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Comparison Group
Comparison Group
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Baseline Characteristics
Baseline Characteristics
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Attrition Rates
Attrition Rates
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Intention-to-Treat Analysis
Intention-to-Treat Analysis
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Generalizability
Generalizability
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Confounding Variables
Confounding Variables
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Inclusion/Exclusion Criteria
Inclusion/Exclusion Criteria
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Exposure and Outcome
Exposure and Outcome
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How is Exposure Measured?
How is Exposure Measured?
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How is Outcome Measured?
How is Outcome Measured?
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Follow-up Period in Cohort Studies
Follow-up Period in Cohort Studies
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Look-back Period in Case-Control Studies
Look-back Period in Case-Control Studies
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Objective Outcome Measures
Objective Outcome Measures
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Appropriate Outcome Measures
Appropriate Outcome Measures
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Adjusting for Confounding Variables
Adjusting for Confounding Variables
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Absolute risk reduction
Absolute risk reduction
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Relative risk ratio (RRR)
Relative risk ratio (RRR)
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Number needed to treat (NNT)
Number needed to treat (NNT)
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Observational study
Observational study
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Black box warning
Black box warning
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Randomized controlled trial (RCT)
Randomized controlled trial (RCT)
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Study Notes
Evaluating Observational Studies
- Observational studies are crucial in medical literature, examining rare events and those taking time to develop. They play a role in comparative effectiveness research, offering a realistic view of daily practice.
- These studies, however, require a critical review due to their inherent variable quality which may threaten internal and external validity. A deep understanding of the study design, its limitations and critical evaluation of the findings are needed. Results should not be automatically accepted; evaluation methods are key.
Objectives
- The extent of bias in observational studies should be explained.
- The necessity for critical appraisal of observational studies needs to be defined.
- Formal criteria for assessing observational studies should be listed.
- Design, methods, and analytical approaches in these studies should be evaluated.
- Results of observational studies should be evaluated alongside randomized controlled trials (RCTs).
Introduction
- Bias and confounding are systemic errors found in the selection, measurement, and analysis of observational study subjects.
- Selection bias is particularly problematic, especially due to lack of randomized treatment assignment. Factors influencing participant in and follow-up of a study can skew results if the selected group is not representative
- Measurement bias (information bias) occurs during data collection. If there are systematic differences between groups in the way exposures or outcomes are measured or reported by participants, caregivers or researchers, it skews results.
Bias and Confounding
- A confounding factor is associated with both the outcome and the treatment, but is not a consequence of the treatment. The factor is not directly related to the treatment.
- Selection bias can happen if confounding factors aren't balanced between treatment and comparison groups.
- Controlling for confounding factors includes observable confounding factors, stratification, statistical adjustment, instrumental variable methods, and Heckman selection models.
General Criteria for Evaluating Observational Studies
- Internal validity assesses the validity of the study's results, while external validity determines how generalizable the results are to local practice.
- STROBE (Strengthening the Reporting of Observational studies in Epidemiology) provides a statement to help researchers evaluate observational studies, as well as equip readers with critical appraisal skills for evidence.
- A checklist for critical assessment includes research question, study design, study population, exposure, outcome, data analysis and confounding, presentation of results, and interpretation of results alongside practice and policy implications
Research Question
- Research questions, including any pre-specified hypotheses, should be clearly stated in the introduction.
- A clear, plausible research question along with its scientific background and rationale is crucial to evaluating observational studies.
- The study should clearly outline the population being studied and the key outcomes of the research
Study Design
- Observational study designs include cohort, case-control, cross-sectional, and case-series (or case reports). These generally need to be applied when the issue is related to the target or source population.
- The choice of design should be appropriate to address the research questions.
Subject Selection
- Determining how subjects were selected is crucial for understanding the generalizability of the results.
- A thorough description of the source population, along with a comparison to the target population relevant to the research question, is necessary.
- Adequate documentation of inclusion and exclusion criteria, and characteristics of the study population are needed. A comparison of those characteristics to patients encountered in clinical practice should be addressed.
- An appropriate comparison group, with a stated justification, is important. The comparison group should be comparable to the treatment group.
- Careful attention should be paid to the response rate as well as any attrition rate over time and the underlying reasons. Appropriate strategies should address or mitigate potential biases and distortions. Intention-to-treat analysis should be used when appropriate.
Exposure and Outcome Measures
- Exposures and outcomes are measured using various reliable methods, such as patient reports, medical records, or pharmacy data. Look-back periods need to be appropriate for case-control studies where assessing long-term outcomes might have delays.
- Clear and complete documentation explaining the processes used to measure exposes and outcomes is crucial. Outcomes should also be measured objectively appropriate to the specific study.
Data Analysis and Confounding
- Statistical tests need to be appropriate for both the design and the measurement of outcome variables. Accounting for rare events and sample size needs to be considered to avoid erroneous conclusions.
- Multivariable regression analysis should be used to adjust for multiple confounding factors - in regards to both continuous and binary data.
- Residual confounding may also be an issue and should be assessed, as it could result from unobservable variables.
Presentation of Results and Interpretation
- The interpretation and conclusion must be supported by the actual study findings.
- Risk ratios, odds ratios, and hazard ratios are commonly used.
- The number needed to treat (NNT) and number needed to harm (NNH) can be reported to help visualize the magnitudes of treatment effects more easily.
- The choice of measure should be documented and justified.
Application to Practice and Policy
- The impact of the findings on clinical practice and public policy should be evaluated.
- Decisions for practice or policies should not be based on one study alone. Well-designed observational studies can complement findings of RCTs, which are more scientifically rigorous as many FDA black-box warnings were largely based on observational studies, not RCTs.
- Evaluations should include considering the availability of RCT data during a study, the differences in populations, and the reliability of exposures and outcomes.
Comparison of Results From Observational Studies and Randomized Trials
- Results from observational studies and RCTs may sometimes differ. This could be due to methodological variations such as differences between study populations, how exposures are measured, and how outcomes are measured.
- Different ways for exposures, outcomes and data collection will influence the outcomes findings. Possible explanations for discordant results should be considered, and the implications for practice should then be assessed.
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Description
This quiz focuses on understanding the critical components necessary for assessing observational studies, including the STROBE statement and external validity. Test your knowledge of designing checklists for evaluation and learn key elements that are essential to research questions. Ideal for students in epidemiology and clinical research.