Systematic Reviews Flashcards
What factors should primary studies have to be indicated in a systematic review?
Transparency, reproducibility, explicity.
Define a systematic review.
An overview of primary studies normally randomised controlled trials that use explicit and reproducible methods but can also be case-control studies or cohort studies.
How are systematic reviews conducted?
Large number of studies initially identified The narrow down to most relevant and credible.
Define meta-analysis.
A quantitative synthesis of the results of multiple primary studies that addressed the same hypothesis in the same way, provides an overall value with associated confidence intervals.
What is publication bias?
Studies were statistically significant or favourable results are more likely to be published to draw in advertisement. This will show in a funnel plot.
What is the fixed effect model for variation?
Assumes the studies in the review are all estimating the same true value, lack of heterogeneity.
What is the random effects model?
Assumes the studies are you estimating similar, but not the same, true effect - use indicated by heterogeneity.
What is the difference between the random and fixed effect models?
Waiting is more evenly distributed in random effects model (ie. more given to smaller studies). This means fixed effect model has tighter confidence intervals.
What problems are there with systematic review and meta-analysis?
Heterogeneity between, variable quality of, and publication bias in selection of, studies.
What are the features of a forest plot?
Individual odds ratios (squares) and confidence intervals (lines) are displayed for each study, size of square proportional to weight given to the study, the diamond is the pooled estimate with its width representing the 95% confidence intervals, solid axis represents the null hypothesis.
How can systematic reviews before the publication bias?
Use published AND unpublished trials.
What are the advantages of systematic reviews?
Explicit methods reduce bias, exclude poor studies, meta-analysis provides overall figure for all included studies, large amounts of information can be assimilated quickly by healthcare professionals, more reliable and accurate.
