Analysis of Mixed Types of Traits in Genetic Association Studies and Application to Genome-Wide Association Studies Open Access
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Genetic association tests aim to test if a genetic marker is associatedwith a trait. There are two common types of traits, one is binary (casecontrol) trait, the other is quantitative (continuous). For a genetic outcome dependent sampling, the binary trait and the quantitative trait are correlated. Since these two types of traits are dependent,so it is more powerful to test a joint association of the genetic marker with the both traits than to just test each single trait separately(Klei et al., 2008; Zhu et al., 2009). In this research, we proposed a simple approach to combine these two mixed types of traits into a single ordinal outcome, then apply a proportional odds model to identify the association between a genetic marker and the mixed types of traits. Performance of these mothods for analysis of mixed types of traits will be evaluated in comparison with existing methods using simulation studies. Application to a genome-wide association study of rheumatoid arthritis with outcome-dependent sampling will be presented.