marginal effects that act jointly with exposure factors [85]. As many more GWAS datasets are expected to be generated in the near future, meta-analyses, which integrate multiple independent GWAS datasets, can be included in gene set analysis methods to increase sample size and power [86]. We hope this review and discussion on the methodological issues on gene set analysis of GWAS will help investigators to find better solutions, understand potential biases, and make gene set analysis more practical and beneficial for understanding genetic variants conferring disease risks in GWAS.
