1. My father has been diagnosed with probable late onset AD and his ApoE test is negative for e4 alleles. Should his doctor be doing other genetic testing?
No, not at this time. Forty percent of those who have late onset AD are negative for ApoE e4 alleles. While genetic
mutations of the PSEN1, PSEN2, and APP genes are associated with AD in a very small number of specific family lines, they are associated with early onset AD, not late onset. If your father did not show signs of AD until after the age of 65, then this other genetic testing is not indicated. If you have a very strong family history of AD, several family members over several generations have had AD, you may want to talk to your father’s doctor about family risk factors.
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2. Should everyone have their ApoE genotype tested?
No, the test is not intended to be used to screen the general population. It is intended to be used in very specific situations to give a doctor additional information. The majority of people have ApoE e3 and so will tend to have normal lipid metabolism. Most of the people with other ApoE combinations will never develop significant problems associated with their lipid metabolism, have type III hyperlipoproteinemia, or develop ApoE associated late onset AD.
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3. Is there a reason to test for ApoE genotype more than once?
No, not unless your doctor suspects that the first test was in error. A person inherits one copy of the
gene from each parent and genotype does not change.
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