[R-meta] converting Odds Ratio to Risk Ratio in CHE model

[Viechtbauer, Wolfgang (NP)]

I totally understand that part, but I am not quite sure which OR values you want to convert. If you fitted a model to standardized mean differences, then one cannot really transform the estimates from such a model to risk ratios (well, maybe, with a lot of creativity, but let's not go there). If you are simply asking how to convert ORs to RRs, then this can be done, but requires assuming a baseline risk. The transf.lnortorr() function in metafor will do this (to be precise, it transforms log odds ratios to risk ratios). For example, say the OR is 2.5. Then the corresponding RR is:

transf.lnortorr(log(2.5), pc=0.10)

2.17, assuming that the baseline risk is 10%. But if the baseline risk is 20%, then

transf.lnortorr(log(2.5), pc=0.20)

shows that the corresponding RR is 1.92.

Best,
Wolfgang

> -----Original Message-----
> From: Sicong Liu <64zone using gmail.com>
> Sent: Thursday, April 18, 2024 13:04
> To: Viechtbauer, Wolfgang (NP) <wolfgang.viechtbauer using maastrichtuniversity.nl>; R
> Special Interest Group for Meta-Analysis <r-sig-meta-analysis using r-project.org>
> Subject: Re: converting Odds Ratio to Risk Ratio in CHE model
>
> Thank you for your response Wolfgang!
>
> I apologize for not being clear and the question is totally motivated by making
> the interpreation easier. The targeted audience of the work is in public health.
> Although OR is  used in this domain,  some people find it difficult to think in
> terms of "odds", which is not as easy as "chance"  interpreted from RR, hence
> the question. Thank you!
>
> Cheers,
> Sicong (Zone)
> -------------
>
> From: Viechtbauer, Wolfgang (NP) <wolfgang.viechtbauer using maastrichtuniversity.nl>
> Date: Thursday, April 18, 2024 at 6:16 PM
> To: R Special Interest Group for Meta-Analysis <r-sig-meta-analysis using r-
> project.org>
> Cc: Liu Sicong <64zone using gmail.com>
> Subject: RE: converting Odds Ratio to Risk Ratio in CHE model
> Dear Sicong,
>
> I don't understand the question (seems to be pattern for me today ...). If you
> converted everything to SMDs, then the results from the model provides estimates
> in terms of this (SMD) measure. So where / why do you want to convert ORs to
> RRs?
>
> Best,
> Wolfgang
>
> > -----Original Message-----
> > From: R-sig-meta-analysis <r-sig-meta-analysis-bounces using r-project.org> On
> Behalf
> > Of Liu Sicong via R-sig-meta-analysis
> > Sent: Wednesday, April 17, 2024 10:07
> > To: r-sig-meta-analysis using r-project.org
> > Cc: Liu Sicong <64zone using gmail.com>
> > Subject: [R-meta] converting Odds Ratio to Risk Ratio in CHE model
> >
> > Dear All,
> >
> > Hope all is well.
> >
> > I have been applying the correlated and hierarchical model (CHE, Pustejovsky &
> > Tipton, 2021) to fitting data consisting of ~98 clinical trials with binary
> > outcomes. The effect sizes took the initial form of odds ratio (OR) and were
> > converted to the standard mean difference (SMD) when fitting the CHE model.
> > Because OR is challenging for interpretation and I wonder if there are ways to
> > transform from OR to risk ratio (RR) when reporting the model parameter
> > estimates? Or, as some literature (see Knol et al., 2012) suggests, converting
> > to RR entails a change of model?
> >
> > Thank you all very much!
> >
> > Pustejovsky, J. E., & Tipton, E. (2022). Meta-analysis with robust variance
> > estimation: Expanding the range of working models. Prevention Science, 23(3),
> > 425-438.
> >
> > Knol, M. J., Le Cessie, S., Algra, A., Vandenbroucke, J. P., & Groenwold, R.
> H.
> > (2012). Overestimation of risk ratios by odds ratios in trials and cohort
> > studies: alternatives to logistic regression. Cmaj, 184(8), 895-899.
> >
> > Best regards,
> > Sicong
> >
> > ------------------------------------------
> > Sicong (Zone) Liu, Ph.D.
> > Professor
> > South China Normal University
> > ------------------------------------------