Impact of family structure on the power of linkage tests using sib-pair methods

This analysis sought to determine the impact of specific ascertainment crit eria based upon nuclear family affectation structures. Specifically, we eva luated the predicted and observed proportion of alleles shared identical by descent conditional on the number of affected and unaffected siblings in a pedigree, and compared sib-pair method linkage results under two ascertain ment schemes, random vs. selected ascertainment, for this simulated complex genetic disease. These results suggest that samples differing in the compo sition of affected and unaffected siblings in the family will differ in the ir power to detect linkage. An effect of sampling scheme on power to map us ing affected-sib-pair methods should be considered when a reported linkage is not found in another study population. ((C)) 1999 Wiley-Liss, Inc.