Stanford Ethics Panel Rejects Genetic Testing for ...
BW 02.06.99 20:09
Stanford Ethics Panel Rejects Genetic Testing for Alzheimer's Disease
Business Editors/Health & Medical Writers
STANFORD, Calif.--(BW HealthWire)--June 2, 1999--Genetic testing for Alzheimer's disease
currently is not appropriate for most people, a Stanford biomedical ethics group has
concluded after studying the issue for nearly two years.
Scientific understanding of the genetics of Alzheimer's disease is advancing rapidly, and
commercial tests are now available for some genes that have been associated with the
disease. In most cases, however, these tests do not provide enough information to be
useful except in research, according to a working group assembled by Stanford's Program in
Genomics, Ethics and Society (PGES).
For nearly two years, the working group grappled with the ethical issues raised by genetic
tests for Alzheimer's. The 38 members are experts in a number of fields, including
medicine, genetics, nursing, psychology, biomedical ethics, and the law. The group
presented the full version of its policy recommendations, along with 17 background papers,
in a special issue of the journal Genetic Testing released last week. Guest editors for
the issue were Laura M. McConnell, former PGES associate director; Barbara A. Koenig, PhD,
co-director of PGES and executive director of the Stanford Center for Biomedical Ethics;
Henry T. Greely, JD, Stanford professor of law and co-director of PGES; and Thomas A.
Raffin, MD, professor of medicine and PGES co-director.
Alzheimer's disease involves a gradual, irreversible deterioration in mental abilities
such as memory and reasoning. Most of the 4 million Americans who have the disease are
over 60. As the American population ages, the number of sufferers is expected to rise and
is projected to reach 10 million by the year 2050.
The introduction of genetic tests for Alzheimer's disease over the past few years has
raised concerns on a wide range of issues, from the impact of knowing one's own genetic
susceptibility to an incurable disease, to the potential for discrimination in access to
long-term care, said Koenig.
The availability of skilled genetic counseling is another serious concern. There are
relatively few trained genetic counselors in the United States, and the need for them is
bound to increase as scientists learn more about the genetics of human disease, said
Greely. "It's not easy to provide good counseling on these issues, and the people who
do it need substantial training not only in genetics but also in the social issues,"
he said.
Genetic testing, said Greely, has two potential applications in Alzheimer's disease:
predicting an asymptomatic person's risk of developing the disease and helping to
establish a diagnosis in a person with symptoms. But the link between Alzheimer's and
genetics has turned out to be very complicated.
Either predictive or diagnostic genetic testing may be appropriate for individuals from
families with a clear pattern of inherited, early-onset Alzheimer's disease, the PGES
working group concluded. But this disease pattern accounts for only a small percentage of
Alzheimer's cases.
Mutations in three genes have been associated with these rare, inherited forms of
Alzheimer's disease. The mutations are considered highly "penetrant," which
means they correlate strongly with the occurrence of the disease. A commercial test is
available for one of the three genes, called presenilin 1 (PS1). PS1 mutations account for
about half the cases of early-onset, familial Alzheimer's disease perhaps 1 percent of all
Alzheimer's cases.
The most common form of Alzheimer's does not show a familial pattern of inheritance.
Numerous studies, however, have linked variations in a gene called APOE with
susceptibility to this "sporadic" form of the disease.
The APOE gene produces a protein called apolipoprotein E, which transports cholesterol in
the blood. Each individual carries two copies of the APOE gene, one from each parent.
There are three versions, or alleles, of the gene, called APOE 2, 3 and 4. People who
carry one copy of a particular version of this gene, APOE4, have an increased risk of
developing the disease. People who inherit the APOE4 allele from both parents run an
especially high risk of developing Alzheimer's disease. However, many individuals with the
disease do not have the APOE4 allele, and people who do carry APOE4 can live to advanced
age without any detectable signs of the disease.
The PGES working group recommended that genetic testing not be used to aid diagnosis of
the sporadic form of Alzheimer's disease. The test improves the accuracy of diagnosis only
slightly, and a positive result does not change prognosis or treatment for the patient.
But for family members, who could learn of their own potential susceptibility from a
relative's test, the results can impose psychological burdens and social costs even if
good genetic counseling is available, the working group argued.
To obtain a copy of Genetic Testing, call Esther Bicovny at Mary Ann Liebert, Inc., the
journal's publisher, at 914/834-3100 ext. 623.
PGES, part of the Stanford Center for Biomedical Ethics, was launched in 1995 with a
three-year unrestricted gift from SmithKline Beecham Corp. Other sources of funding for
PGES include the Arnold and Mabel Beckman Foundation and the United States Department of
Energy.
--30--pw/sf* ao/sf
CONTACT: Stanford
Mitchell Leslie, 650/725-5371 (Media)
mleslie@leland.stanford.edu
Henry T. Greely, JD, 650/723-2517 (Comment)
Barbara Koenig, PhD, 650/725-6103 (Comment)
KEYWORD: CALIFORNIA
INDUSTRY KEYWORD: MEDICINE BIOTECHNOLOGY
Today's News On The Net - Business Wire's full file on the Internet
with Hyperlinks to your home page.
URL: http://www.businesswire.com
Copyright 1999 Business Wire. All rights reserved.