Model-free sib-pair linkage analysis: Combining full-sib and half-sib pairs

When sampling full-sibs for linkage studies, half-sibs are often available. Not only are half-sibs convenient to sample, but they can sometimes offer greater power than full-sibs. We propose a method to combine the informatio n from full-sibs and half-sibs into a single test for linkage. This method is based on the Haseman and Elston [1972] method of regressing the squared trait-difference for a pair of sibs (either full- or half-sibs) on the esti mated proportion of alleles shared identical by descent. To approximate the distribution of the test statistic, we propose a correction factor that co nsiders the correlation among sibs, and demonstrate by simulations that thi s approximation works well in many situations, although there are some cond itions for which the statistic can have an inflated Type-I error rate. The main appeal of our proposed method is the speed at which it can be computed , offering a rapid way to perform genome-wide linkage screens. Genet. Epide miol. 19:30-51, 2000. (C) 2000 Wiley-Liss. Inc.