I was reading this interesting paper: Ten simple rules for conducting umbrella reviews
and this phrase caught my attention:
An exact conversion of an effect size into an equivalent OR may not always be possible, because the measures of effect size may be inherently different and the calculations may need data that may be unavailable. […] Fortunately, approximate conversions are relatively straightforward. On the one hand, the analysts may assume that HRs, IRRs, RRs and ORs are approximately equivalent as far as the incidence is not too large
Does anyone have a reference for this statement? I couldn’t find a paper discussing the magnitude of the incidence to consider it “not too large”. I also always thought that HR and RR (or OR) are different estimators and the conversion between them is not possible but maybe I miss something. I would like to hear your thoughts about it
Thank you!
gma