Applications of the concept of attributable fraction in medical genetics.

Attributable fraction, the fraction of cases of a disease in a population attributed to a particular risk factor, is a useful measure in the design and interpretation of epidemiologic studies of disease etiology. We review here the applications of the concept of attributable fraction in medical genetics. Specifically, attributable fraction can be used 1) in studies of the association between genetic traits and specific diseases to quantitate the contribution of specific alleles to disease occurrence in a population; 2) in population studies of mutations and birth defects to estimate the impact of mutagens and teratogens; and 3) in genetic analyses of family data, to evaluate the contribution of putative single gene loci to disease etiology. In the latter context, the concept of attributable fraction can be contrasted with the more commonly used concept of heritability. Examples from the literature provide illustrations of the usefulness of attributable fraction in medical genetic studies.