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. 2021 Feb 1;190(2):318-321.
doi: 10.1093/aje/kwaa167.

Do Case-Control Studies Always Estimate Odds Ratios?

Jeremy A Labrecque, Myriam M G Hunink, M Arfan Ikram, M Kamran Ikram

Do Case-Control Studies Always Estimate Odds Ratios?

Jeremy A Labrecque et al. Am J Epidemiol. .

Abstract

Case-control studies are an important part of the epidemiologic literature, yet confusion remains about how to interpret estimates from different case-control study designs. We demonstrate that not all case-control study designs estimate odds ratios. On the contrary, case-control studies in the literature often report odds ratios as their main parameter even when using designs that do not estimate odds ratios. Only studies using specific case-control designs should report odds ratios, whereas the case-cohort and incidence-density sampled case-control studies must report risk ratio and incidence rate ratios, respectively. This also applies to case-control studies conducted in open cohorts, which often estimate incidence rate ratios. We also demonstrate the misinterpretation of case-control study estimates in a small sample of highly cited case-control studies in general epidemiologic and medical journals. We therefore suggest that greater care be taken when considering which parameter is to be reported from a case-control study.

Keywords: case-control studies; control sampling; incidence rate ratio; odds ratio; risk ratio.

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