A COMPARATIVE-STUDY OF SIBSHIP TESTS OF LINKAGE AND OR ASSOCIATION/

Population-based tests of association have used data from either case- control studies or studies based on trios (affected child and parents) . Case-control studies are more prone to false-positive results caused by inappropriate controls, which can occur if, for example, there is population admixture or stratification. An advantage of family-based t ests is that cases and controls are well matched, but parental data ma y not always be available, especially for late-onset diseases. Three r ecent family-based tests of association and linkage utilize unaffected siblings as surrogates for untyped parents. Im this paper, we propose an extension of one of these tests. We describe and compare the four tests in the context of a complex disease for both biallelic and multi allelic markers, as well as for sibships of different sizes. We also e xamine the consequences of having some parental data in the sample.