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Related Experiment Videos

Linkage disequilibrium testing when linkage phase is unknown.

Daniel J Schaid1

  • 1Department of Health Sciences Research, Mayo Clinic/Foundation, Rochester, Minnesota 55905, USA. Schaid@mayo.edu

Genetics
|March 17, 2004
PubMed
Summary
This summary is machine-generated.

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Accurate measurement of linkage disequilibrium is crucial for understanding human genome structure and traits. A composite statistic by Weir and Cockerham offers reliable error rates, outperforming the common likelihood-ratio statistic in simulations.

Area of Science:

  • Genetics
  • Statistical Genetics
  • Bioinformatics

Background:

  • Linkage disequilibrium (LD) measures nonrandom allele association at different loci, vital for haplotype structure and trait association studies in the human genome.
  • Unobserved haplotype phase in unrelated subjects complicates LD measurement and significance testing, necessitating statistical methods that handle this ambiguity.
  • The likelihood-ratio statistic is commonly used for LD testing but assumes Hardy-Weinberg equilibrium, potentially leading to biased error rates.

Purpose of the Study:

  • To evaluate the statistical performance of methods for measuring linkage disequilibrium when haplotype phase is unknown.
  • To compare the accuracy and power of the likelihood-ratio statistic against a composite statistic proposed by Weir and Cockerham.
  • To extend the composite statistic for multi-allelic loci and assess its utility.

Related Experiment Videos

Main Methods:

  • Simulations were employed to assess the type I error rates and power of different statistical methods for linkage disequilibrium.
  • The performance of the likelihood-ratio statistic was evaluated under conditions where Hardy-Weinberg equilibrium may not hold.
  • A composite statistic was simulated and compared, with extensions developed for loci having more than two alleles.

Main Results:

  • Simulations demonstrated that the likelihood-ratio statistic can exhibit significantly biased type I error rates (either too conservative or too liberal).
  • The composite statistic proposed by Weir and Cockerham maintained correct type I error rates across simulations.
  • The composite statistic showed comparable power to the likelihood-ratio statistic and proved effective when extended for multi-allelic loci.

Conclusions:

  • The likelihood-ratio statistic's assumption of Hardy-Weinberg equilibrium can lead to unreliable results in linkage disequilibrium testing.
  • The Weir and Cockerham composite statistic provides a more robust and accurate method for testing linkage disequilibrium with unknown haplotype phase.
  • The extended composite statistic is a strong alternative for global linkage disequilibrium assessment, especially in complex genetic datasets.