This test is to detect the presence of the APOE4 variant, which is associated with increased risk of late-onset (age >60-65) Alzheimer’s disease (AD). Testing may be considered for patients with dementia to supplement information from clinical and other evaluations. This test is not appropriate for children. APOE genotype results are E2/E2, E2/E3, E2/E4, E3/E3, E3,E4, or E4/E4. APOE genotyping supplies supplementary information for the clinical diagnosis of Alzheimer’s disease.
Apolipoprotein (Apo) E is produced under the direction of the APOE gene and is one of five main types of blood lipoproteins (A-E). This test evaluates a person’s DNA to determine what combination of APOE forms (genotype) is present. The APOE gene exists in three different forms (alleles) – e2, e3, and e4 – with e3 being the most common allele, found in 60% of the general population. Everyone inherits a pair of APOEgenes that is some combination of these three.
APOE e4 has been associated with an increased risk of late onset Alzheimer disease (AD), that is AD that develops after the age of 65. This effect is additive in that one copy of e4 (e2/e4 or e3/e4) carries some increased risk and two copies of e4 (e4/e4) are associated with even more of a risk of developing AD. It is important to note, however, that we are talking about the risk relative to other people at the same age with fewer copies of e4. In terms of lifetime risk, most individuals with APOE e4 will never develop AD and there are many people with AD who are e4 negative.