systematic review and meta-analysis Flashcards
what is the hierarchy of evidence?
what is a review?
A ‘review’ is the generic term for any attempt to synthesise the results and conclusions of two or more publications on a given topic.
what are the different types of reviews?
1) Traditional literature reviews/narrative reviews
2) Systematic reviews (with or without meta‐analysis/ meta-synthesis)
why is a narrative reviw not sufficent?
– bias arising from the studies included in the review
– bias arising from the studies not included in the
review
– bias arising from the way the review is done.
E.g. just including the papers which support your existing view point and ignoring those which don’t.
what is a systematic review?
- summary of medical literature
- uses explicit and reproduceible methods to systematically search, critically appraise and synthesize on a specific issue
- synthesises the results of multipple research studies
- reduces bias and random erors
what are the aims of a systematic review?
– Systematic (e.g. in its identification of literature)
– Explicit (e.g. in its statement of objectives, materials and methods)
– Reproducible (e.g. in its methodology and conclusions)
compare and contrast systematic vs narrative literaure reviews
why are desicions about systematic reviews made at the outset?
So that retrospective decision-making does not bias findings
where can you register your research protocol so that others dont do the same research as you?
PROSPERO
What things should you think about when formulating the research question?
what method is used to evaluate
what is the structural framework that is udsed to write a systemic review using qualatative studies and mixeed research?
outline the step by step process of a systemic review
- Well-formulated question
- Comprehensive database search
- Unbiased selection and abstraction process
- Critical appraisal of selected studies
- Synthesis of data and interpretation of results (evidence synthesis)
what is an example of the application of SPIDER?
what is inclusion criteria?
this is a criteria for the type of papers you wil be looking at and the criteria you have as a minum for inclusion into your review
Inclusion criteria – relate exactly to your PICO(ST)/ SPIDER criteria plus dates of studies and language of publication
what is exclusion criteria?
Exclusion criteria – clearly delineate which studies will not or should not be included
what is the benefit of having clear inclusion and exclusion criteria?
ensures that similar studies are being compared- so youre not comparing apples and oranges
what is a good tool for appraising bias in RCTs?
Cochrane Risk of Bias tool / CONSORT
what is a good tool for appraising observational studies?
STROBE
what is the PRISMA statement?
this is a checklist of items that need to be reported in a systmaic review
what are limitations of systematic reviews?
• There may be no trials/evidence
– If you apply all your criteria effectively and get <5 studies, this is fine!
• Lack of good quality evidence is a finding…
The trials may be of poor quality
Results may still be inconclusive
Practice does not change just because you have the evidence of effect/effectiveness
define meta analysis
the statistical technique involved in extracting and combining quantitative data to produce a summary result.
what is meta-synthesis?
efers to a group of methods used to synthesise qualitative (or mixed) data to produce a summary result/ a re-analysis of previous studies/study findings.
strength of meta- analysis
Effect of an intervention is seen over a bigger sample size than possible in a single trial
- Results of each study are weighted for sample size
- Results from a range of settings can be compared
- Can evaluate homogeneity of results, i.e. variability of effect sizes
- Can explore variability, i.e. test moderators of effect size (e.g. study quality)
what are weaknesses of meta-analysis?
Heterogeneity – studies which measure things differently are difficult to combine, orcombination becomes meaningless: “apples and oranges”
Publication bias – examine with funnel plot- this is when only papers with positive results are published so you dont get the full picture
Requires a lot of effort and subject-area expertise
Mechanics of statistics may obscure theory
