Genetic analysis of late-onset diseases using first-degree relatives.

We consider the problem of testing that a disease with variable age at onset is an autosomal dominant or recessive genetic trait. Specific reference is made to Alzheimer's disease and recent publications proposing an autosomal dominant inheritance pattern. The pedigree structure allowed is restricted to first-degree relatives of the proband for the dominant and to sibs of the proband for the recessive hypotheses, respectively, in addition to the proband. The sampling method assumed is the one most often used in practice: single ascertainment or sampling pedigrees with probability proportional to size (pps), i.e., to the number of affected individuals within a pedigree who are in the sampling frame. The statistical methodology developed takes the sampling procedure into account and is a generalization of the Kaplan-Meier method of estimating survival functions to pps sampling.