[R-meta] Results interpretation publication bias

[Wilma Charlott Theilig]

Hey all,

I am currently conducting my first meta-analysis using a random effects model. I wanted to investigate whether there is publication bias in my studies using different small-study effects methods. Egger's test and rank correlation test indicate funnel plot asymmetry. I then used the trim and fill method twice. Once with all studies and since I had a very high I2 value (98.4%) and then again but with excluded outliers (here I used the find.outlier function from dmetar to identify 39 of 79 studies as outliers) as a sensitivity analysis. Both values are higher (r= .57 and r= .38 without outliers) than than the original overall pooled effect size (r= .36). So my interpretation would be: there seems to be "missing" mainly large effect sizes with small standard errors (i.e. large studies reporting large effect sizes, at least according to the contour enhanced funnel plot). But maybe it is also due to high heterogeneity? How can I interpret this result? I would greatly appreciate an answer and some help.

Best regards

Wilma

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