Reviews of Evidence Flashcards
Describe the limitations of using evidence from individual studies
Problems with interpretation due to variations in sampling and generalisability
Explain the circumstances in which a systematic review should be undertaken and its purpose
b
Define a meta-analysis
A quantitative synthesis of the results of two or more primary studies that addressed the same hypothesis in the same way
Interpret this Forest plot
Describe what it is showing
Each square in an individual odds ratio for each study with the 95% CIs as the lines
Size of square= weight given to the study
♦Diamond= pooled estimate
…Dotted line= pooled odds ratio
Width of diamond= pooled 95% CIs
Solid line= null hypothesis odds ratio
List the common difficulties in systematic reviews and meta-analyses
Heterogeneity between studies
Variable quality of studies
Publication bias in selection of studies
Describe a meta-analysis
It allows the quantification of effect sizes and their uncertainty as a pooled estimate
Displayed as a forest plot
How can we try to overcome the effects of variable qualities of studies used to perform a meta-analysis?
Define the basic quality standard and only include those that meet this criteria
Score each study for its quality to…
- incorporate this into the weighting
- use sub-group analyses to explore the differences
What are the main components of assessing the qualities of RCTs during a meta-analysis?
Allocation methods
Blinding and outcome assessment
Patient attrition
Appropriate statistical analysis
Describe the effect of publication bias
How can it be shown to exist or not?
Publication bias leads to biased selection of studies towards demonstration effect
Can be shown to exist or not on a FUNNEL plot
Define a systematic review
An overview of primary studies that used explicit and reproducible methods
Describe a systematic review
Has a clear focused questions (formal protocol)
Explicitly states type of study, participant, intervention and outcome measures
What are the key features of a systematic review that make it an extremely credible source of evidence?
Explicit
Transparent
Reproducible
What are the two groups of sub-group analysis?
Stratification by study characteristics - whole studies
Stratification by participant profile - type of participant
