Understanding genetic testing for Alzheimer disease: medical and epidemiological background

Defining dementia: social and historical background of Alzheimer disease

Though Alzheimer disease (AD) has been recognized as a distinct entity since 1907, scientific understanding of, and public interest in, the disease remained very limited until the 1970s. The perception of AD as a significant problem has been substantially affected by cultural and demographic changes and by interest group and federal government initiatives. The recognition of AD has transformed senility from an expected stage of life into a "disease." It has also increased fear both of the individual effects of having AD and of the social consequences of AD in the population. Both the biotechnology industry and AD activist organizations will play a role in the social implications of genetic testing for AD.

The genetics of Alzheimer disease and the application of molecular tests

Two general classes of genes are associated with the development of Alzheimer disease (AD). The first group consists of genes that appear to cause AD when mutated, and the second category is composed of genes that are statistically associated with AD, depending on the inheritance of specific alleles. This paper reviews the current state of knowledge about the genetics of AD, and we then discuss the two molecular tests that are currently commercially available. These include a genetic test for mutations in the presenilin 1 (PS1) gene that can diagnose or predict a subset of early onset familial AD with a high degree of certainty. The value of the genetic test for the apolipoprotein (APOE) allele status is far less clear. Inheritance of the epsilon 4 allele is associated with an increased risk of AD at a population level, but APOE genotyping is inappropriate for prediction of future disease in an individual and offers only a marginal increase in diagnostic certainty when symptomatic individuals are tested. In the future, genetic tests may become more broadly applicable to the diagnosis and prediction of AD. However, the utility of such tests is currently limited to a small subset of individuals because in the vast majority of AD cases no clear genetic or environmental cause has been defined.

High school genetics education and Alzheimer disease

Improved and updated human genetics education, including Alzheimer disease (AD) awareness and education, is urgently needed. National, state, and local standards for science education agree that human genetics, biotechnology applications, and the social and ethical issues raised by modern technology need to be taught in high school science using hands-on and inquiry methods of teaching. High school science courses are the last opportunity for most individuals to learn human genetics. There are an increasing number of new and successful human genetics curriculum materials and inservice teacher education programs at the secondary school level aligned with national and state science education standards. These curricula and teacher education programs can be enhanced by collaborative partnerships of geneticists, genetics professionals, biotechnology scientists and technical personnel, and science educators, several of which are in successful operation. Because human genetics involves families and generations, genetics education tied to AD may provide a unique opportunity to educate two generations, both students and parents, to the many medical, personal, family, community, and cultural issues of human genetics and genetic conditions. Implementing human genetics and AD education provides a recipe for accurate, relevant, sustainable and exciting teaching and learning for all involved.

Genetic testing and Alzheimer disease: recommendations of the Stanford Program in Genomics, Ethics, and Society

Several genes associated with Alzheimer disease (AD) have been localized and cloned; two genetic tests are already commercially available, and new tests are being developed. Genetic testing for AD--either for disease prediction or for diagnosis--raises critical ethical concerns. The multidisciplinary Alzheimer Disease Working Group of the Stanford Program in Genomics, Ethics, and Society (PGES) presents comprehensive recommendations on genetic testing for AD. The Group concludes that under current conditions, genetic testing for AD prediction or diagnosis is only rarely appropriate. Criteria for judging the readiness of a test for introduction into routine clinical practice typically rely heavily on evaluation of technical efficacy. PGES recommends a broader and more comprehensive approach, considering: 1) the unique social and historical meanings of AD; 2) the availability of procedures to promote good surrogate decision making for incompetent patients and to safeguard confidentiality; 3) access to sophisticated genetic counselors able to communicate complex risk information and effectively convey the social costs and psychological burdens of testing, such as unintentional disclosure of predictive genetic information to family members; 4) protection from inappropriate advertising and marketing of genetic tests; and 5) recognition of the need for public education about the meaning and usefulness of predictive and diagnostic tests for AD. In this special issue of Genetic Testing, the PGES recommendations are published along with comprehensive background papers authored by Working Group members.