Statistical designs for familial aggregation

In the past two decades, it has become increasingly clear that genetic fact ors contribute to the aetiology of many common diseases including cancers, coronary disease, allergy and psychiatric disorders. While one goal of gene tic epidemiological studies is to locate susceptibility genes for these com plex diseases, it is important that strong evidence of familial aggregation be established at an early stage of research. In this paper, we discuss se veral study designs useful to address some issues such as (1) detecting fam ilial aggregation, (2) testing for gene-environment interaction, (3) identi fying homogeneous subgroups and (4) measuring magnitude and patterns of fam iliar correlations. These designs include the conventional case-control des ign and the family case-control design. For each of these two study designs , we discuss analytical strategies as well as their strengths and weaknesse s. Throughout, several examples from real studies are used for illustrative purposes.