Systematic Reviews Flashcards
What are systematic reviews?
- Review of all literature
- On one particular topic/question
- Using scientific methods
Reasons for differences between RCTs
- Chance
- Differences in people
- Differences in intervention/comparator
- Differences in care other than that being investigated
- Differences in the way treatment effects are assessed
- Differences in follow-up
- Reporting of the available evidence
- Selection from the available evidence
What is publication bias?
When publication of research results depends on their nature and direction
Types of publication bias
- Positive result bias
- Outcome reporting bias
What is positive result bias?
When authors are more likely to submit, or editors accept, positive than negative or inconclusive results
What is outcome reporting bias?
When several outcomes within a trial are measure but are reported selectively depending on the strength and direction of those results
Issues systematic reviews attend to
- Large volume of information
- Low-quality information drowns out high-quality?
- Cannot find/read the right evidence for the specific needs
- Must critically evaluate the methodological rigor and statistically analyse each study
Review definition
Any attempt to summarise information
Benefits of reviews
- Volume of literature condensed
- New information made accessible
- Some have taken considerable time to find all info + review topic well
Hierarchy of evidence for effectiveness (top to bottom)
- Systematic reviews
- RCTs
- Cohort studies
- Case control studies
- Case series’ + reports
- Expert opinion, “anecdotal” evidence
Stages in a systematic review
- Define question
- Write protocol
- Search for evidence/studies
- Select relevant evidence
- Appraise studies
- Extract, analyse + summarise data
- Interpret review results
- Discussion + conclusion
What criteria are used to define the question for a systematic review?
PICO:
- Population
- Intervention
- Comparison
- Outcome
What is a meta-analysis?
Statistical technique used to combine the quantitative results from a number of studies
Advantages of a systematic review
- Can be best source of evidence
- Assimilation of large amounts of research
- Provide reliable, unbiased estimates of effect
- Increase precision of estimates of effect
- Provide info about generisability + consistency of effect
- Identify what info is missing
- Useful for making decisions
What is internal validity?
Degree to which the effect of the observed is attributable to the evidence, rather than any other cause
