Would you recommend genetic testing for the APOE4 allele in family members of an Alzheimer disease ...

Background:
There are two forms of Alzheimer disease (AD): one with a strong familial pattern of inheritance, characterized by early onset; a second sporadic form with a late onset. The familial form of AD is caused by mutations in any of three genes associated with the production and processing of the amyloid beta-protein AD1 . However, less than 5 of all cases can be traced to genetic causes. The sporadic, late-onset form of AD is a complex disorder resulting from a number of genes, multiple environmental factors, and epigenetic mechanisms. Only one such gene that confers an enhanced risk for AD has been identified. This gene, Apolipoprotein E (APOE), encodes a protein involved with cholesterol metabolism, transport, and storage. The APOE gene has three alleles (E2, E3, and E4). Those who are homozygous for the APOE4 allele have a 10- to 15-fold increased lifetime risk of developing AD.