The Quantitative LOD Score: Test Statistic and
Sample Size for Exclusion and Linkage of Quantitative
Traits in Human Sibships
Page GP, Amos CI, Boerwinkle E
Human Genetics Center, University of Texas School of Public Health, M.D.
Anderson Cancer Center, Houston, TX 77030, USA.
American Journal of Human Genetics, 62(4):962-968 (1998).
Abstract
We present a test statistic, the quantitative LOD (QLOD) score, for the testing of
both linkage and exclusion of quantitative-trait loci in randomly selected human
sibships. As with the traditional LOD score, the boundary values of 3, for
linkage, and -2, for exclusion, can be used for the QLOD score. We investigated
the sample sizes required for inferring exclusion and linkage, for various
combinations of linked genetic variance, total heritability, recombination
distance, and sibship size, using fixed-size sampling. The sample sizes required
for both linkage and exclusion were not qualitatively different and depended on
the percentage of variance being linked or excluded and on the total genetic
variance. Information regarding linkage and exclusion in sibships larger than size
2 increased as approximately all possible pairs n(n-1)/2 up to sibships of size 6.
Increasing the recombination (theta) distance between the marker and the trait
loci reduced empirically the power for both linkage and exclusion, as a function
of approximately (1-2theta)4.
Variance component linkage analysis