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When to Select Observational Studies Quiz
- 1. When To SelectObservational Studies Interactive Quiz Prepared for: The Agency for Healthcare Research and Quality (AHRQ) Training Modules for Systematic Reviews Methods Guide www.ahrq.gov
- 2. When should observationalstudies be considered for inclusion in a comparative effectiveness review? Observational studies should never be considered for inclusion. Observational studies should always be considered for inclusion as the default strategy. Observational studies should be included only when there is sufficient evidence from randomized controlled trials (RCTs) to confirm the validity of RCT findings. Using Observational Studies in Comparative Effectiveness Reviews
- 3. Which of thefollowing is the first question to consider when deciding whether or not to include observational studies in assessments of benefits? Will trials provide valid and useful information to address key questions? Are there gaps in the available observational evidence? Are there gaps in trial evidence for the review questions under consideration? Using Observational Studies in Comparative Effectiveness Reviews
- 4. A comparative effectivenessreview to compare percutaneous coronary intervention with coronary artery bypass graft for coronary disease identified 23 randomized controlled trials. Your Technical Expert Panel has raised concerns that these 23 trials enrolled patients with a relatively narrow spectrum of disease relative to those having the procedures in current practice. What should you do? Change your key questions to focus on the types of patients for whom research is available. Complete your review, including only the 23 trials that were identified. Expand your review to include observational studies. Observational Studies and Applicability of the Comparative Effectiveness Review
- 5. Once gaps inthe trial evidence to assess benefits have been established and you have decided to include observational studies, which of the following should you do? Include all suitable observational studies found to answer the initial key questions. Exclude trial data that can be answered by the selected observational studies. Refocus the study question on the gaps in trial evidence. When Observational Studies Are Needed
- 6. In the absenceof sufficient trial data, which types of observational studies should routinely be searched for and included in comparative effectiveness reviews as evidence of harms? Case reports Cross-sectional studies Cohort and case-control studies What Types of Observational Studies Are Best for Assessing Harms?
- 7. What is confoundingby indication? A type of detection bias A type of attrition bias A type of selection bias Assessing Bias in Observational Studies
- 8. Observational studies shouldalways be considered for inclusion in comparative effectiveness reviews (CERs). When considering whether to include observational studies in assessments of benefits, determine first if there are gaps in the trial evidence under review. When assessing harms in comparative effectiveness reviews, investigators should routinely include cohort and case-control studies. Once gaps in trial evidence to assess benefits have been established and the decision has been made to include observational studies, reviewers should refocus study questions on the gaps in trial evidence and look for observational studies that address the gaps. Studies with a high risk of bias due to confounding by indication are usually not suitable for inclusion in CERs. Summary
- 9. This quiz wasprepared by Dan Jonas, M.D., M.P.H., and Karen Crotty, Ph.D., M.P.H., members of the Research Triangle Institute – University of North Carolina Evidence-based Practice Center. The module is based on chapters 4 and 8 in version 1.0 of the Methods Guide for Comparative Effectiveness Reviews (available at: http://www.effectivehealthcare.ahrq.gov/ehc/products/60/294/2009_0805_principles1.pdf). Authors
Editor's Notes
- #2 When To Select Observational Studies Interactive Quiz
- #3 Using Observational Studies in Comparative Effectiveness Reviews When should observational studies be considered for inclusion in a comparative effectiveness review? Incorrect. Observational studies should always be considered for inclusion as the default strategy. Correct. Observational studies should always be considered for inclusion as the default strategy. Incorrect. Observational studies should always be considered for inclusion as the default strategy.
- #4 Using Observational Studies in Comparative Effectiveness Reviews Which of the following is the first question to consider when deciding whether or not to include observational studies in assessments of benefits? Incorrect. Trials generally provide valid and useful information and are the first source of evidence when selecting data for inclusion in a comparative effectiveness review (CER). The second question to consider when deciding to include observational studies in CERs is whether or not observational studies provide valid and useful information to address key questions. Incorrect. Whether there are gaps in the observational evidence is not the first consideration when selecting evidence. Correct. The first of two steps when considering whether or not to include observational studies is to determine whether there are gaps in the trial evidence under review.
- #5 Observational Studies and the Applicability of the Comparative Effectiveness Review A comparative effectiveness review (CER) to compare percutaneous coronary intervention with coronary artery bypass graft for coronary disease identified 23 randomized controlled trials. Your Technical Expert Panel has raised concerns that these 23 trials enrolled patients with a relatively narrow spectrum of disease relative to those having the procedures in current practice. What should you do? Incorrect. The lack of trial data is not a reason to change prespecified key questions that were developed to answer an important clinical question. Incorrect. You should consider the advice from your TEP suggesting that the evidence to date poorly represents clinical practice and will result in poor applicability of the results of your CER. Correct. Expanding your review to include suitable observational studies will improve the applicability of your CER.
- #6 When Observational Studies Are Needed Once gaps in the trial evidence to assess benefits have been established and you have decided to include observational studies, which of the following should you do? Incorrect. You should include observational studies that address the gaps in trial evidence. Incorrect. You should not exclude suitable trial data. Correct. You should refocus the study questions on gaps in trial evidence and search for observational studies that address those gaps.
- #7 What Types of Observational Studies Are Best for Assessing Harms In the absence of sufficient trial data, which types of observational studies should routinely be searched for and included in comparative effectiveness reviews (CERs) as evidence of harms? Incorrect. Case reports are hypothesis generating rather than hypothesis testing. Although they may be a good source of information for planning future research and may provide some preliminary data on new drugs for which nothing else is available, they may often not provide an adequate level of evidence to warrant inclusion in a CER. Incorrect. Cross-sectional studies are typically hypothesis generating. Cohort and case-control studies are well suited for testing hypotheses of whether one intervention is associated with a greater risk for an adverse event than another and for quantifying that risk. These studies should routinely be included in CERs for evidence of harms. Adjudicating with a third reviewer is the best way to ensure the most accurate results. Correct. Cohort and case-control studies are well suited for testing hypotheses that one intervention is associated with a greater risk for an adverse event than another and for quantifying that risk. These studies should routinely be included in CERs for evidence of harms.
- #8 Assessing Bias in Observational Studies What is confounding by indication? Incorrect. Detection bias refers to systematic differences in outcome assessments among comparison groups. This type of bias can often be minimized through study design and appropriate implementation. Incorrect. Attrition bias refers to systematic differences among comparison groups in the loss of participants from the study and their loss of being accounted for in results. For both trials and observational studies, large attrition rates introduce a serious risk of bias, which may render the results invalid. Correct. Confounding by indication is a type of selection bias that occurs when study groups differ because they have different diagnoses, severity of illness, or comorbid conditions and are assigned different treatments, which thereby introduces systematic differences into the comparison groups. It is often difficult to adjust for confounding by indication in analyses; therefore, studies with a high degree of this type of potential bias are usually not suitable for inclusion in a comparative effectiveness review.
- #9 Summary
- #10 Authors This interactive quiz augments the module on selecting observational studies. This quiz was prepared by Dan Jonas, M.D., M.P.H., and Karen Crotty, Ph.D., M.P.H., members of the Research Triangle Institute – University of North Carolina Evidence-based Practice Center. The module is based on chapters 4 and 8 in version 1.0 of the Methods Guide for Comparative Effectiveness Reviews (available at: http://www.effectivehealthcare.ahrq.gov/ehc/products/ 60/294/2009_0805_principles1.pdf).