[R-meta] Subgroup analysis output using metafor - interpretation

[Guido Schwarzer]

Am 09.01.20 um 15:26 schrieb Joao Afonso:
> [...]
> As for the outliers I could take a step back and instead of removing them
> leave them in the data-set and see what happens when conducting the
> sub-group analysis. Is this best practice when conducing a meta-analysis?

I am no expert on outlier detection (in meta-analysis), however, I would 
say that it is in general a good idea to try to explain between-study 
heterogeneity using subgroup analysis or meta-regression first.

An intrinsic feature / problem of the meta-analysis of prevalences is 
typically the substantial between-study heterogeneity (which is clearly 
visible in your meta-analysis with an I2 of 99.7%). In my view, the main 
aim of a prevalence meta-analysis is actually to describe this 
heterogeneity. Removing outliers would reduce this heterogeneity and 
paint a different picture. I assume that there will be still substantial 
heterogeneity after conducting subgroup analyses. Prediction intervals 
can help to properly describe the between-study heterogeneity.

Best wishes, Guido