Systematic reviews Flashcards
Systematic review
aims to answer a defined research question by collecting and summarising empirical evidence that fits prespecified eligibility criteria
What do systematic reviews provide
More generalisable conclusions
Comprehensive summary of knowledge
Advantages of systematic review
Transparent inclusion of studies
MA increases power of study
May identify lack of adequate evidence
Stage 1 of systematic review
Planning the review
Define research question
Stage 2 of a systematic review
Identification of research (search criteria and thorough search)
Selection of studies (with inclusion and exclusion criteria)
Study quality assessment (establish whether bias exists)
Stage 3 of a systematic review
Reporting and dissemination
Details and effect estimate abstracted
Estimate overall effect by combining data
if meta-analysis is appropriate
Meta analysis
Integrates results of studies matching eligibility criteria
Generates a pooled risk estimate
Advantages of a meta analysis
More subjects included= more reliable
Differences (heterogeneity) between studies can be identified
If studies are too heterogeneous
May be inappropriate to pool results
Forest plot
graph of results from each study included in a systematic review, together with the combined meta- analysis result
What is each study represented by on a forest plot?
Box and line
What does the size of the box in a forest plot signify?
The weight of the study
What does the horizontal line in a forest plot signify?
95% confidence interval
What does the diamond in a forest plot signify?
The overall estimate of the meta analysis
“pooled point estimate”
What does the centre of the diamond and dashed line in a forest plot signify?
Summary effect estimate
What does the width of the diamond in a forest plot signify?
The confidence interval around this estimate
Publication bias
greater likelihood of research with statistically significant results to be published
What can show publication bias?
Funnel plots
What do funnel plots indicate?
whether there is a link between study size (or precision) and the effect estimate
Heterogeneity
Studies trying to answer the same question may still differ with respect to the exact population, interventions/exposure, outcomes & designs used
Even when factors are homogeneous
heterogeneity may still exist
because of clinical differences, methodological differences or unknown study characteristics.
How to explore heterogeneity
Galbraith (radial) plots
Limitations of systematic reviews
If too few studies matching eligibility criteria, a systematic review might not add much.
Inadequate methodological quality of studies can compromise findings of reviews
Publication bias can distort findings