I am writing a meta-analysis looking at the correlation between different tests for assessing body composition.

The results of the studies that I have included use different ways to calculate the correlation, including linear regression ($R^{2}$), Pearson's $r$, concordance correlation coefficient (CCC), and mean difference (SD) + 95% CI.

I would like to compare these results. I have found that I can take $\sqrt{R^{2}}$ to get $r$. Is there also a way to calculate $r$ from CCC? Or is CCC so similar to Pearson's $r$, that I can just call it $r$ and throw everything on one pile?