Genetic screening: Implications for preventive medicine

Genetic screening is a search for persons in a population who possess certain genotypes: that are associated with existing disease or predispose to future disease: that may lead to disease in their descendants; or that produce other variations of interest but not known to be associated with disease. This concept is not quite encompassed in an earlier and well-respected document on screening for disease. It is obviously relevant to citizens living in industrialized societies who have benefited from traditional practices in public health. It has become a conventional public health exercise to screen bloods of newborns for the hyperphenylalaninemias, the tyrosinemias, the amino acidopathies in general, the galactosemias, and the aberrations of thyroid hormone biosynthesis; and to screen urines for disorders of amino acid or monosaccharide metabolism and transport. Screening of young adults to initiate genetic counseling for indications of Tay-Sachs, β thalassemia, and sickle cell heterozygosity has also become a common practice in the relevant high-risk ethnic communities. Screening to identify persons with variant phenotypes, such as α1-antitrypsin deficiency, has become a form of epidemiologic research to discover the natural history of the variant. Each of the screening modes presupposes that a risk to health can be identified and that something can be done to prevent disease or to understand better the predisposition to disease. The nature of disease from a biological viewpoint and the particular relevance of genetic screening in a modern world are discussed.