Data-dredging gene-dose analyses in association studies: biases and their corrections.

To examine the joint effect of multiple loci on disease risk, many case-control association studies used "gene-dose analyses." However, some researchers defined high-risk genotypes (or alleles) as those that have higher genotypic (allelic) frequencies in the case group compared with the control group in the study. This will lead to the total number of the "high-risk" genotypes (alleles) tending to be higher for the cases than for the controls as well, even if none of the studied loci were related to the disease. Monte-Carlo simulations done in this study showed that such a "data-dredging" gene-dose analysis could produce grossly biased results. A permutation correction method was proposed which could correct the biases very effectively.