Forest Plots in meta analysis

Question 1

What is the role of forest plots?

Answer 1

• visually present the results of individual studies and their effect sizes
• provide a comprehensive summary of the data allowing researchers to assess the overall treatment effect and the heterogeneity among studies
• essential tool for academics to combine information from various articles into a single image
• makes it possible for us to compare immediately what the studies reveal and te wuality of the results in one location

Question 2

What is on the horizontal axis of a forest plot?

Answer 2

• represents the statistic the studies being profied
• can be a relative stats likes an odds ratio or a relative risk (relative reduction) (RR)
• or absolute risk reduction
• or standardised mean difference

Question 3

What is shown on the vertical axis of a forest plot?

Answer 3

• the line of null effect
• placed at the value where there is no association between an epxosure and outcome or no difference betwen two interventions

Question 4

What are the componenets of a forest plot?

Answer 4

• a black box - reflects a point estimate of the study result. size of the study is also shown by this black box
• the bigger the box, the more participants in the study
• horizontal line - represents the 95% confidence intervals for the study’s results with each end of the line serving as the boundaries of the intervals

Question 5

What does the diamond represent on forest plots?

Answer 5

s- represents point estimate and confidence intervals when you combine and average all the individual studies together
- rules about crossing the line of null effect are still true here
- if horizontal tips of the diamond cross the vertical line, the combined result is potentially not statistically significant

Question 6

How to check heterogeneity of papers?

Answer 6

• I2 stats
• the I2 should be less than 50%
• anything higher = papers may be inconsistent due to some reason other than chance