Solved – How to go about doing Egger’s test for publication bias in a meta-analysis

publication-bias

Hi my background is clinical medicine (not statistics). I have just done a meta-analysis of 41 randomized controlled trials of the effectiveness of antibiotics vs. placebo in preventing wound infection. I used Review Manager 5.3 software for the data analysis (dichotomous data, random effects model), calculated the effect estimates as Odds Ratios (with 95% CI), and have already constructed a funnel plot within Revman for publication bias. I was then advised to do Egger's test to more accurately assess publication bias. There is no facility for that in Revman, does anyone know of an (inexpensive or free) stats program I can use? I am not sure how to do it 'by hand', but will try if not too complex. Any Advice welcome.
Thanks!

Best Answer

An option is to use the free statistical software R (link). I generally use the metafor package, but there are also other packages out there that can be used for this purpose (see this page for more information about R packages related to meta-analysis).

An example using the metafor package:

install.packages("metafor") # Install metafor package

library(metafor) # Load metafor package

dat <- dat.bangertdrowns2004 # Use these data as example

res <- rma(yi = yi, vi = vi, data = dat) # Random-effects meta-analysis

regtest(res) # Conduct Egger's test

Regression Test for Funnel Plot Asymmetry

model:     mixed-effects meta-regression model
predictor: standard error

test for funnel plot asymmetry: z = 2.4904, p = 0.0128

?regtest # Description of the function in the metafor package

It might be important to realize that the rma() function by default uses the restricted maximum likelihood estimator (REML) for estimating the between-study variance in a meta-analysis. If Review Manager is using a different estimator for the between-study variance, you may also get slightly different results. You can, however, specify the estimator for the between-study variance in the rma() function. See ?rma for more information.

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