Systematic reviews and meta-analyses Flashcards
What is the role of systematic reviews and meta analyses in evidence based practice?
They provide a structured summary of research results prepared and executed using well-defined and precise methodologies.
The systematic review is often but not always accompanied by meta-analysis which is a statistical analysis of the combined results of these studies.
What is a systematic review?
Review of clearly formulated question which uses relevant research to answer the question.
The review uses systematic and explicit methods to identify, select, and critically appraise relevant research and to collect and analyze data from the studies included.
What is the objective of systematic reviews?
Comprehensive and trustworthy means of synthesizing the literature.
Prepared very systematically with explicit, transparent, and predefined methods to limit bias.
Results can be summarized from quantitative, qualtitative or a combination of both studies.
Meta-analysis is not necessary but can provide a statistical summary of the results. If no meta analysis then review is synthesized in words.
What can systematic reviews synthesize?
Quantitative studies (meta analysis / narrative synthesis)
Qualitative studies (aggregate or integrate findings from primary qualitative research studies into themes or metaphors)
Quantitative and qualitative studies (mixed methods review)
What are the advantages of systematic reviews?
Improve the dissemination of evidence
Hasten assimilation of research into practice
Assist in clarifying the heterogeneity of conflicting results between studies
Establish generalisability of the overall findings
Improve the understanding of a particular phenomenon or situation
Can guide decision making
Can set a research agenda
What kinds of systematic reviews should be used for discussing the effectiveness of interventions?
Systematic reviews of RCTs (Most common type)
What kind of systematic reviews should be used for questions about diagnosis?
Synthesis about the accuracy of the test or instrument
What kind of systematic reviews should be used for questions about prognosis?
Synthesis of cohort studies for questions about prognosis
What do systematic reviews of qualitative studies allow us to do?
To have a more comprehensive understanding of patients’ experience and views
How are systematic reviews located?
Can be difficult due to large volume of research.
Cochrane Database of Systematic Reviews is the premier source for systematic reviews of intervention effectiveness
DARE: Database of abstracts of reviews of effects
Specialist evidence databases
Discipline-specific databases
Large biomedical databases (using a systematic review filter)
How is a systematic review conducted?
Requires a significant and dedicated time commitment, varying depending on the number of citations/abstracts involved.
Involves many steps:
- Formulate a question
- Define eligibility criteria for the systematic review
- Conduct the search for studies
- Screen studies for inclusion
- Review full-texts of eligible studies
- Assess the risk of bias
- Abstract the data
- Meta-Analysis (if being done)
What is included in a meta-analysis?
Generate estimates and Confidence Intervals
Rate confidence in estimates
How is the research question defined?
Should be clearly focused and defined using PICO
Should make sense clinically and be worth answering
When should decision be made about the methods for searching, screening, appraisal and synthesis?
Before commencing review.
How are the eligibility criteria determined for a systematic review?
Using explicit, predefined criteria for including and excluding studies.
Eligibility criteria for systematic reviews of the effects of interventions have focused on defining types of participants, types of interventions and comparisons and types of studies.
How are potentially eligible studies found?
Search methodology should be clearly explained and reproducible.
Multiple databases must be searched and citation tracking must be used.
How is publication bias avoided in systematic reviews?
Locate studies that have not already been published and ongoing or planned studies in the area. (contact authors and doctoral theses) this is to avoid publication bias.
After finding studies what is done to refine the studies to what is important?
The eligibility criteria set before are applied to selected studies to be included in the review.
At least 2 authors select papers.
Titles and abstracts are screened for relevance and eligibility
A final evaluation of the full-text articles is conducted and a decision is made on whether to include or exclude the studies.
How is bias avoided in selecting papers?
During the refining process at least 2 authors must do the selection process to eliminate selection bias.
How is the risk of bias assessed in a systematic review?
2 or more people independently extract data and judge the likely risk of bias.
A risk-of-bias tool is used.
What information is extracted from included studies in a systematic review?
Participants
Intervention
Outcome measures used
Results of study
Study methodology and risk of bias
This is all standardised and used to summarize the data.
What must be evaluated for a meta-analysis?
The intervention effect, including confidence intervals is calculated for each of the studies.
Overall intervention effect is calculated.
Why may a meta-analysis not be possible?
Because the individual studies may not be similar enough in one or more respects.
Forest plots may still be presented but without an overall estimate and/or results are described narratively.
What is a meta-analysis?
A statistical technique that enables data from multiple studies to be combined as a new dataset.
It includes larger sample size and more events than any one study.
Principle output is a forest plot.
What does a forest plot tell us? What are its components?
The compiled data of several studies are put onto one big graph.
Each horizontal line with a square in the middle represents the results of a different study.
Square is called the point estimate (result of a particular study)
Size of the point estimates echoes the length of the confidence interval.
Diamond is called a summary estimate. (summary of the weighted results from the combined studies)
Vertical line in the center is the line of no effect (if result touches it or crosses it then the result is not statistically significant)
What are the steps of critically appraising quantitative systematic reviews?
- Methods: The validity of the review methodology
- Results: The magnitude and precision of the intervention effect
- Applicability: Of the review to your patient or population
A checklist can be used to guide this process. (eg CASP, AMSTAR)
What are the reporting statements (checklists) used for quantitative and qualitative reviews?
Quantitative: PRISMA
Qualitative (ENTREQ)
What do reporting statements contain?
PRISMA contains 27 steps for authors to ensure all important information is present.
ENTREQ uses a 21 step checklist
