Special issues in genetic testing for Alzheimer disease.

Genetic testing for Alzheimer disease (AD) raises two issues that are, thus far, unusual. First, genetic testing of dementia patients for diagnostic purposes necessarily leads to information of some predictive significance for the patient's family members. What information about the test results should be disclosed to whom needs careful consideration. Testing for a patient's apolipoprotein E (APOE) allele status was used, both in research and clinically, as a predictor of cardiovascular risk long before it was known to be associated with AD risk. Whether and how information about the newly understood AD implications of the test should be provided to those who were tested for cardiovascular risk needs attention, as does the general problem of new, and possibly less benign, meanings for old genetic test results.