[R-meta] Between study correlation between two different outcomes

[Aulbach, Matthias B]

Hi,

I am conducting a meta-analysis, using the great metafor package. I have run into the problem of dependency when using more than one outcome from the same set of studies. In an earlier attempt, I had run two univariate meta-analyses and then used the outcome of one outcome as a predictor in a meta-regression with the other outcome as the dependent variable. But that ignores the within-study correlation between the two, so I'd like to improve that. So I'd like to handle that using a multivariate meta-analysis, using rma.mv and this line of code (with yi denoting the effect sizes, vi their standard errors, type_outcome the kind of outcome that was measured, and ID as the study identifier):

rp <- rma.mv(yi, vi, data=pd, mod = ~ factor(type_outcome) -1, random= ~ type_outcome | ID)

This nicely gives me the different effects for the two kinds of outcomes. However, what I am so desperately interested in is the between-study correlation between the two outcomes, i.e. if there's a strong effect on one outcome, is there also a strong effect on the other (or not)? Is there a way to get that information, including confidence intervals and a significance test for the correlation coefficient?

Any kind of advice is deeply appreciated!

Best,

Matthias


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