Interpreting Meta-Analyses A Guide to Funnel and Forest Plots

Meta-analyses represent the best available medical evidence. Although a powerful tool, they are not without criticisms since any bias in the original studies are then compounded when they are pooled together for the meta-analysis. Funnel plots provide a useful graphical representation of the presence of bias, and forest plots represent the heterogeneity of findings within studies included in a meta-analysis. The purpose of this review is to help readers interpret these statistical tools to better understand the findings of a meta-analysis.