Journal Article

Ascertainment Bias in Family-based Case-Control Studies

Kimberly D. Siegmund and Bryan Langholz

in American Journal of Epidemiology

Published on behalf of Johns Hopkins Bloomberg School of Public Health

Volume 155, issue 9, pages 875-880
Published in print May 2002 | ISSN: 0002-9262
Published online May 2002 | e-ISSN: 1476-6256 | DOI:
Ascertainment Bias in Family-based Case-Control Studies

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In a family-matched case-control study, a population-based sample of cases is selected from a well-defined geographic region over a fixed period of time. For diseases of adult onset, the control is generally a sibling or cousin who is matched on sex and age without regard to location of residence. Such a design can lead to biased estimates of environmental relative risk if the prevalence of an environmental risk factor varies by the geographic region from which the cases and controls are drawn. However, assuming the independence of genotype and environmental exposure, the estimators for the gene and gene-environment interaction effects are consistent. This suggests that we must use caution in interpreting parameters that estimate environmental main effects from a family-based case-control study if controls are selected from outside the case-ascertainment region.

Keywords: bias; case-control studies; family relations; USC, University of Southern California

Journal Article.  3900 words.  Illustrated.

Subjects: Public Health and Epidemiology

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