Systematic Reviews Flashcards
Give three factors that can be used to assess quality of an RCT.
Was it randomised?
Was there blinding of the outcome assessment?
Intention to treat used?
Define inclusion and exclusion criteria? baseline comparability Defined primary outcome Sample size calculation Good follow up and adequate length
What is the difference between a systematic review and a meta-analysis?
Why may a systematic review not include a meta-analysis?
Systematic review = overview of primary studies that used explicitly and reproducible methods.
Meta-analysis = quantitative synthesis of the results of two or more primary studies that addressed the same hypothesis in the same way
If there is too much heterogeneity in the studies.
What does the diamond represent in a forest plot?
What does the size of the square represent?
Diamond = pooled estimate
- Centre indicated pooled odds ratio
- Width represents pooled 95% CI
Weight given to the study
What 2 factors determine the weight given to a study?
Size of confidence interval
Sample size
Give 3 problems with meta analysis.
Heterogeneity between studies
Variable quality of studies
Publication bias in selection of studies
What are two ways to fix heterogeneity between studies to allow for them to combined?
Modelling for variation
Analysing the variation.
Describe the fixed effects model.
Assumes there is one true fixed effect size and that all studies that deviate from this do so due to random error.
Give some differences in fixed and random effects models.
More weights to smaller studies in random effects model
95% CI usually wider in the random effects model
Point estimate is often similar
What is used to minimise publication bias?
Describe this process.
Funnel plot analysis
Funnel plot = study size against effect measure (OR for example)
Symmetrical
