Statistical validity of the Haseman-Elston sib-pair test in small samples

Area of Science:

• Genetics
• Biostatistics
• Statistical genetics

Background:

• The Haseman-Elston sib-pair test is a common method for detecting linkage between genetic markers and quantitative traits.
• Evaluating the statistical validity of this test, particularly in smaller sample sizes, is crucial for accurate genetic analysis.

Purpose of the Study:

• To determine the empiric type I error rate of the Haseman-Elston sib-pair test in samples with 60 or fewer sib pairs.
• To assess the impact of marker-locus heterozygosity on the test's statistical validity.

Main Methods:

• Simulation experiments were conducted to evaluate the type I error rate.
• The Haseman-Elston test was applied to a quantitative trait and five unlinked markers.
• Two different methods for calculating degrees of freedom for the t-distribution were used and compared.

Main Results:

• Empiric type I error rates were slightly liberal when degrees of freedom were calculated based on the number of sib pairs per sibship (sigma s(i)(s(i) - 1)/2 - 2).
• When degrees of freedom were based on the number of sibs minus 1 per sibship (sigma (s(i) - 1) - 2), estimated empiric p-values closely matched nominal p-values.
• Reduced marker-locus heterozygosity did not elevate the empiric type I error rate in small samples.

Conclusions:

• The Haseman-Elston sib-pair test demonstrates acceptable statistical validity for linkage analysis in small sample sizes when appropriate degrees of freedom are used.
• The choice of degrees of freedom significantly impacts the test's type I error rate, with sigma (s(i) - 1) - 2 being more accurate.
• Marker heterozygosity levels do not compromise the test's reliability in small sample settings.