Abstract
Objective
Recently Doi et al. argued that risk ratios should be replaced with odds ratios in
clinical research. We disagreed, and empirically documented the lack of portability
of odds ratios, while Doi et al. defended their position. In this response we highlight
important errors in their position.
Study design and setting
We counter Doi et al.’s arguments by further examining the correlations of odds ratios,
and risk ratios, with baseline risks in 20,198 meta-analyses from the Cochrane Database
of Systematic Reviews.
Results
Doi et al.’s claim that odds ratios are portable is invalid because 1) their reasoning
is circular: they assume a model under which the odds ratio is constant and show that
under such a model the odds ratio is portable; 2) the method they advocate to convert
odds ratios to risk ratios is biased; 3) their empirical example is readily-refuted
by counter-examples of meta-analyses in which the risk ratio is portable but the odds
ratio isn't; and 4) they fail to consider the causal determinants of meta-analytic
inclusion criteria: Doi et al. mistakenly claim that variation in odds ratios with
different baseline risks in meta-analyses is due to collider bias. Empirical comparison
between the correlations of odds ratios, and risk ratios, with baseline risks show
that the portability of odds ratios and risk ratios varies across settings.
Conclusion
The suggestion to replace risk ratios with odds ratios is based on circular reasoning
and a confusion of mathematical and empirical results. It is especially misleading
for meta-analyses and clinical guidance. Neither the odds ratio nor the risk ratio
is universally portable. To address this lack of portability, we reinforce our suggestion
to report variation in effect measures conditioning on modifying factors such as baseline risk; understanding such variation is essential
to patient-centered practice.
Keywords
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Article info
Publication history
Published online: August 11, 2021
Accepted:
August 4,
2021
Received:
June 1,
2021
Identification
Copyright
© 2021 Elsevier Inc. All rights reserved.
