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Adjusting for selection bias in retrospective, case-control studies

Geneletti, Sara, Richardson, Sylvia and Best, Nicky (2008) Adjusting for selection bias in retrospective, case-control studies. Biostatistics, 10 (1). pp. 17-31. ISSN 1465-4644

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Identification Number: 10.1093/biostatistics/kxn010


Retrospective case–control studies are more susceptible to selection bias than other epidemiologic studies as by design they require that both cases and controls are representative of the same population. However, as cases and control recruitment processes are often different, it is not always obvious that the necessary exchangeability conditions hold. Selection bias typically arises when the selection criteria are associated with the risk factor under investigation. We develop a method which produces bias-adjusted estimates for the odds ratio. Our method hinges on 2 conditions. The first is that a variable that separates the risk factor from the selection criteria can be identified. This is termed the “bias breaking” variable. The second condition is that data can be found such that a bias-corrected estimate of the distribution of the bias breaking variable can be obtained. We show by means of a set of examples that such bias breaking variables are not uncommon in epidemiologic settings. We demonstrate using simulations that the estimates of the odds ratios produced by our method are consistently closer to the true odds ratio than standard odds ratio estimates using logistic regression. Further, by applying it to a case–control study, we show that our method can help to determine whether selection bias is present and thus confirm the validity of study conclusions when no evidence of selection bias can be found.

Item Type: Article
Official URL:
Additional Information: © 2008 The Authors
Divisions: Statistics
Subjects: H Social Sciences > HA Statistics
Date Deposited: 28 Jan 2011 14:36
Last Modified: 03 Jun 2024 16:06

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