Summarizing the Evidence and Meta-analysis

Question 1

describe the types of reviews

Answer 1

• systematic review: uses explicit and rigorous methods to identify, critically appraise and synthesize relevant studies
• narrative reviews: summaries of research that lack explicit descriptions of systematic methods
• meta-analysis: quantitative review using statistical analyses
• meta-ethnography: systematic review of qualitative data

Question 2

describe a meta-analysis

Answer 2

• meta-analysis is a statistical technique for combining the findings from independent studies
• meta-analysis is most often used to assess the clinical effectiveness of healthcare interventions; it does this by combining data from two or more randomized control trials
• meta-analysis of trials provides a precise estimate of treatment effect, giving due weight to the size of the different studies included

Question 3

summarize the hierarchy of studies

Answer 3

Question 4

contrast narrative reviews vs. systematic reviews

Answer 4

Question 5

describe the functions of meta-analysis

Answer 5

• identifies heterogeneity in effects among multiple studies and, where appropriate, provide summary measure
• increases statistical power and precision to detect an effect

Question 6

describe the fixed effect vs random effect model

Answer 6

• fixed effect model: assumes each study answers exactly the same question, and thus has the same effect size, so results differ only by chance
• random effect model: assumes studies address different but related questions, and thus the real effect size varies slightly between studies

results differ for 2 reasons: by chance as in a fixed effect model and also because of study characteristics

Question 7

summarize fixed effects model vs random effects model

Answer 7

Question 8

explain how to read a Forest plot

Answer 8

Question 9

explain funnel plots

Answer 9

• funnel plots are a way of assessing whether the results of a review have been influenced by “publication bias”
• if the plot is symmetric, like an inverted V, this is interpreted as demonstrated that there is probably no publication bias
• if the plot is asymmetric, the interpretation is that publication bias is likely