For datasets with evidence for publication bias, the “Duval and Tweedie's Trim and Fill” procedure(10) was used to impute the number of potentially-missing studies. In the absence of bias, the funnel plot would be symmetric with respect to the summary effect. If there are more small studies on the right than on the left, some studies may be missing from the left. The Trim and Fill procedure imputes these missing studies, adds them to the analysis, and then re-computes the adjusted overall effect size.
