Genetic Linkage Analysis of a Qualitative Trait Incorporating an Associated Quantitative Trait

• Activity Number: 458
• Type: Invited
• Date/Time: Thursday, August 7, 2003 : 10:30 AM to 12:20 PM
• Sponsor: Biometrics Section
• Author(s): Jian Huang*+
• Companies: University of Iowa
• Keywords: linkage ; likelihood ; dichotomous trait ; quantitative trait ; variance components ; combined analysis

Abstract

Many complex diseases are usually considered as dichotomous traits but are also associated with quantitative biological markers or risk factors. For such dicotomous traits, if the associated quantitative trait is also linked to the chromosomal regions linked to the dichotomous trait, then joint analysis of dichotomous and quantitative trait should be more efficient than considering them separately. Previous studies have focused on the situation when a dichotomous trait can be modeled by a threshold process acting on a single liability distribution. However, for many complex disorders, diagnosis is generally based on a set of binary or discrete criteria. These traits cannot be modeled based on a threshold process acting on an underlying continuous trait. We propose a likelihood-based method that combines such a discrete trait and an associated quantitative trait in the analysis using affected sib-pair data. Our simulation studies suggest that joint analysis increases the power to detect linkage of dichotomous traits. We also apply the new method to an asthma genome scan data set and incorporate the total serum immunoglobulin E (IgE) level in the analysis.