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The main problems in drawing causal inferences from epidemiological case-control studies are confounding by unmeasured extraneous factors, selection bias and differential misclassification of exposure. In genetics the first of these, in the form of population structure, has dominated recent debate. Population structure explained part of the significant +11.2% inflation of test statistics we observed in an analysis of 6,322 nonsynonymous SNPs in 816 cases of type 1 diabetes and 877 population-based controls from Great Britain. The remainder of the inflation resulted from differential bias in genotype scoring between case and control DNA samples, which originated from two laboratories, causing false-positive associations. To avoid excluding SNPs and losing valuable information, we extended the genomic control method by applying a variable downweighting to each SNP.

Original publication

DOI

10.1038/ng1653

Type

Journal article

Journal

Nat Genet

Publication Date

11/2005

Volume

37

Pages

1243 - 1246

Keywords

Adolescent, Bias (Epidemiology), Case-Control Studies, DNA, Diabetes Mellitus, Type 1, False Positive Reactions, Genetics, Population, Genotype, Great Britain, Humans, Lymphocytes, Models, Genetic, Polymorphism, Single Nucleotide