Prerequisite for conversion from odds ratio to relative risk to be valid

as question, since we can do the conversion from odds ratio (p1/q1)/(p2/q2) to relative risk (p1/(p1+q1))/(p2/(p2+q2)) fairly easily, I wonder if there is anything that I need to pay attention before doing this?

It is obvious that if I am doing a case-control study, I shouldn’t do a conversion, because I never know the relative risk from this kind of study, but anything other things that I need to consider?

Thanks.

Answer

In a sense, odds ratios are more universal than risk ratios so we spend too much time on risk ratios. Risk ratios are incapable of being constant over a wide range of risks, whereas an odds ratio is capable of being constant. For example, if a risk ratio is 3, the starting risk level cannot exceed 1/3. Because of this, models stated in terms of odds ratios often contain fewer interaction terms than models for relative risk (or for risk difference).

Attribution
Source : Link , Question Author : lokheart , Answer Author : Frank Harrell

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