A score test for linkage analysis of ordinal traits based on IBD sharing

Area of Science:

• Genetics
• Statistical genetics
• Bioinformatics

Background:

• Traditional linkage analysis methods are established for binary and quantitative traits.
• Many diseases, such as cancer and psychiatric disorders, are measured on ordinal scales.
• Existing latent variable models for ordinal traits offer higher power but are computationally intensive.

Purpose of the Study:

• To develop a computationally efficient statistical method for linkage analysis of ordinal traits.
• To compare the power and efficiency of the new method against existing approaches.
• To identify genetic loci associated with alcohol dependence using the developed method.

Main Methods:

• Derivation of a computationally efficient score statistic based on identity-by-descent sharing.
• Simulation studies to evaluate the test statistic's distribution and power.
• Application of the method to the Collaborative Study on the Genetics of Alcoholism data.

Main Results:

• The proposed score test is computationally more efficient than the likelihood ratio test.
• Simulation studies confirmed the test's validity and power across different heritability levels.
• A significant linkage signal for alcohol dependence was identified on chromosome 4.

Conclusions:

• The developed score statistic provides a powerful and computationally efficient tool for linkage analysis with ordinal traits.
• This method enhances the ability to map genes for complex diseases measured on discrete scales.
• The findings suggest a specific chromosomal region associated with genetic susceptibility to alcohol dependence.