[R-meta] From Risk Difference to Odds Ratio

[Bernard Fernou]

Hi everyone
I am conducting a meta analysis regarding the relationship between the
presence of organophosphates and obesity in metafor. Our IV is mostly
reported as dichotomous so, as obesity is also dichotomous, we have decided
to perform a meta-analysis of odds ratio.

However, some authors reported adjusted associations using risk difference.
We have contacted these authors to access raw data but we have not received
any response yet. Therefore, our plan was to try to convert this risk
difference in odds ratio.

To do so,  we started from the fact that risk difference is equal to 1/NNT.
Then, we convert this NNT in odds ratio using the formula provided in the
Cochrane Handbook (link is provided below). The assumed control risk was
estimated using the proportion of cases with obesity in the "control" group
(we believe this is feasible since the study is cross sectional). We plan
to perform sensitivity analyses with different assumed control risk.

Would it make sense or should we simply exclude this study?

Thank you for your help

BF

https://handbook-5-1.cochrane.org/chapter_12/12_5_4_3_computing_absolute_risk_reduction_or_nnt_from_an_odds.htm

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