Systematic reviews Flashcards
Systemic reviews can be conducted for what
Any primary study design/ research question
What is a systemic review
A type of literature review that uses systematic methods to collect secondary data, critically appraise research studies, and synthesize studies
What is a systemic review designed to provide
To provide a complete, exhaustive summary of current evidence relevant to a research question
Systemic reviews of what are thought to be key to evidence based medicine
Randomized controled trials
Systemic reviews vs single studies
Save readers time
Provide reliable evidence
-By providing a unbiased comprehensive picture of body of evidence
Resolve inconsistencies
Identify gaps
-Acts a catalyst for a better designed prim. study
Identify when questions have been fully answered
Explore difference between studies
What does a systemic review use
Robust methods to reduce bias in the gathering, summarizing, presenting, interpreting, and reporting of the research evidence
What are the characteristics of a systematic review
1.Well formulated question
- Comprehensive data search
- Unbiased selection and abstraction process
4.Assessment of papers
5.Synthesis of data
What are non-systematic reviews susceptible to and why
Bias
The authors may not clearly state the methodology used, and may be selective in presenting evidence to support a particular, pre-existing view
Why are SR’s important
Reduce large quantities of information into manageable portions
Formulate policy and develop guidelines
Efficient use of resources
Increased power/precision in your estimates
Limit bias and improve accuracy
What is the process of systematic reviews
Authors
-Two or more
-Topic expert
-Methodological expert
Study protocol
0In advance set out what they plan to do methodologically
Specific Question
-Using PICO
Search strategy.
-comprehensive and repeatable
-multiple electronic databases
-published and unpublished literature
-ideally without language restrictions
Inclusion/Exclusion criteria
Specific
Agreed in advance
Critical Appraisal
Systematic and thorough
Risk of Bias
Synthesis
Qualitative (narrative) synthesis
Quantitative pooling of data in meta-analysis,
relative precision and quality of the included studies.
How reliable are SR’s
Depends
-Methodological quality of included studies
-Quality of the Systematic Review itself
-How well was the review conducted?
Whats the exact process of SR’s
- Well formulated question (PICO)
- Comprehensive data search
- Unbiased selection and abstraction process
- Assessment of papers
- Synthesis of data
What does PICO stand for
Participants
-Who is the review interested in studying
Interventions (Exposure)
-What is the intervention or group of interventions of interest
Comparisons
-What will the interventions be compared to
Outcomes
-Which outcomes will tell you which intervention is most effective
What do you do in comprehemsive data search
Needs to be as comprehensive as possible
Consider:
-Electronic databases
-Reference lists
-Hand searching
-English language/non-English language
-Sources of ongoing and/or unpublished studies
What reporting bias’s are there
Statistically significant ‘positive’ results are:
more likely to be published
-publication bias
more likely to be published rapidly
-time lag bias
more likely to be published in English
-language bias
more likely to be cited by others
-citation bias
How to make sure unbiased selection
Data extraction to a predefined data extraction form
Process should be conducted independently by at least two reviewers
Clear description of reasons for exclusion if any
Adequate description of included studies
Details of studies funding sources
What is meant by assessment of papers and how is it carried out
How well the studies have been designed and conducted
Process should be conducted independently by at least two reviewers
What can assessment of papers be used for
As a threshold for inclusion of studies
As a possible explanation for differences in results between trials
In sensitivity analyses
As weights in statistical analysis of the results
What is the preffered quality assessment tool of papers
Component approach
-assesses relevant methodological aspects individually (e.g. randomisation, blinding, drop-outs)
What is the problematic quality assessment tool of papers
Composite scales
What does bias determine
The extent to which results of studies can be believed
In a RCT what are you looking at in a risk of bias assessment
The sequence generation
The allocation concealment
The blinding
Incomplete outcome data
Selective outcome reporting
Other (funding source/ compliance, eg)
In a study risk of bias table what do fill in
Whether there is bias in parts of studies and then you put in something like
-Unclear risk
-Low risk
-High risk
And then a sentance to support judgement
What cab be an explanation for heterogeneity between results of different studies
Variation of risk of bias
