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AuthorSuhail A., Doi
AuthorFuruya-Kanamori, Luis
AuthorXu, Chang
AuthorLin, Lifeng
AuthorChivese, Tawanda
AuthorThalib, Lukman
Available date2020-11-17T05:19:45Z
Publication Date2020-11-07
Publication NameJournal of Clinical Epidemiology
Identifierhttp://dx.doi.org/10.1016/j.jclinepi.2020.08.019
Citation: Doi SA, Furuya-Kanamori L, Xu C, Lin L, Chivese T, Thalib L, Questionableutility of the relative risk in clinical research: A call for change to practice, Journal of ClinicalEpidemiology (2020), doi:https://doi.org/10.1016/j.jclinepi.2020.08.019
ISSN08954356
URIhttps://www.sciencedirect.com/science/article/pii/S0895435620311719?v=s5
URIhttp://hdl.handle.net/10576/16985
AbstractBackground and Objectives In clinical trials, the relative risk or risk ratio (RR) is a mainstay of reporting of the effect magnitude for an intervention. The RR is the ratio of the probability of an outcome in an intervention group to its probability in a control group. Thus, the RR provides a measure of change in the likelihood of an event linked to a given intervention. This measure has been widely used because it is today considered a measure with “portability” across varying outcome prevalence, especially when the outcome is rare. It turns out, however, that there is a much more important problem with this ratio, and this paper aims to demonstrate this problem. Methods We used mathematical derivation to determine if the RR is a measure of effect magnitude alone (i.e., a larger absolute value always indicating a stronger effect) or not. We also used the same derivation to determine its relationship to the prevalence of an outcome. We confirm the derivation results with a follow-up analysis of 140,620 trials scraped from the Cochrane. Results We demonstrate that the RR varies for reasons other than the magnitude of the effect because it is a ratio of two posterior probabilities, both of which are dependent on baseline prevalence of an outcome. In addition, we demonstrate that the RR shifts toward its null value with increasing outcome prevalence. The shift toward the null happens regardless of the strength of the association between intervention and outcome. The odds ratio (OR), the other commonly used ratio, measures solely the effect magnitude and has no relationship to the prevalence of an outcome in a study nor does it overestimate the RR as is commonly thought. Conclusions The results demonstrate the need to (1) end the primary use of the RR in clinical trials and meta-analyses as its direct interpretation is not meaningful, (2) replace the RR by the OR, and (3) only use the postintervention risk recalculated from the OR for any expected level of baseline risk in absolute terms for purposes of interpretation such as the number needed to treat. These results will have far-reaching implications such as reducing misleading results from clinical trials and meta-analyses and ushering in a new era in the reporting of such trials or meta-analyses in practice.
Languageen
PublisherElsevier
Subjectbinary effect measure
relative risk
odds ratio
risk difference
posterior probability
TitleControversy and Debate: Questionable utility of the relative risk in clinical research: Paper 1: A call for change to practice
TypeArticle
Open Access user License http://creativecommons.org/licenses/by/4.0/
dc.accessType Open Access


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