Similarly as in this question, I'm working with meta-analysis of studies reporting ORs of an event.
I have one study where I'm not sure if it should be excluded.
The frequencies of the outcome are: No outcome: 85% Outcome 1: 6% Outcome 2: 9%
Authors use 'multivariate multinomial logistic' regression using this outcome and report adjusted effects as RRR. This estimates refer to continuous variable coded 1 to 4 and range from 1.14 to 2.97 in different models and would be the estimated pooled to meta-analysis.
I know that in case of rare events (sometimes quoted as <10% incidence), RRs approximate ORs.. My question is – would that hold for multinomial model? And is 9% + 6% still rare? Effectively - can these RRRs be use as approximation of ORs?