S6 Reviews Of Evidence Flashcards
What are narrative reviews?
Implicit assumptions, not reproducible therefore biased
What are systematic reviews?
Explicit assumptions, transparent, methodology, reproducible therefore unbiased
What is involved in a systematic review?
An overview of primary studies that used explicit and reproducible methods
Gives explicit statements about the types of study, participants and outcome measures.
What is a meta-analysis?
A quantitative synthesis of results of two or more primary studies that addressed the same hypothesis in the same way
What is the purpose of a meta-analysis?
To facilitate the synthesis of a large number of study results.
To reduce problems of interpretation.
To quantify effect sizes and their uncertainty as a pooled estimate
What problems does a meta-analysis have?
Heterogeneity between studies
Variable quality of studies
Publication bias in selection of studies
Give the two statements you can use in an exam when describing if a result is statisticallysignificant or not
Null hypothesis (1.00) is within the CI, p>0.05, results are not statistically significant.
Null hypothesis (1.00) is outside the CI, p<0.05, results are statistically significant and not due to chance.
What are the features of a forest plot?
Squares are the OR (larger sq for larger weight)
Diamond is the pooled estimate
Dotted line is pooled OR
Solid line is null hypothesis OR (if squares on are either side of this, p>0.05 and data is not significant)
There are two approaches to calculating the pooled estimate OR and its 95% CI, describe the fixed effect model
Assumes the studies are estimating the SAME true effect size
There are two approaches to calculating the pooled estimate OR and its 95% CI, describe the random effects model
Assumes the studies are estimating SIMILAR true effect size.
Weighting is more equal in this.
What are some causes of variable quality?
Poor study design, poor design protocol, poor protocol implementation.
How can we reduce variation?
Have a basic quality standard and only include studies satisfying this criteria
Why does publication bias occur?
Studies with statistically significant /‘favourable’ results are more likely to be published than those studies with ‘unfavourable’ results
What are the consequences of publication bias?
Systematic review or meta-analysis can be flawed by PB
What methods of identification are used for publication bias?
Check meta-analysis protocol for method of identification of studies, Plot against a measure of size e.g funnel plot, Use a statistical test for PB
