Test Summary

Quest AD-Detect® Apolipoprotein E (ApoE) Isoform, Plasma - Apolipoprotein E (ApoE) is a well-defined genetic risk factor for late-onset Alzheimer's disease (AD). The human APOE gene has three polymorphic alleles, E2, E3 and E4 that result in six different genotypes: E2/E2, E2/E3, E3/E3, E2/ E4, E3/E4 and E4/E4. About half of AD patients carry the E4 allele (compared with 14% in the general population), with the majority being heterozygotes (E3/E4). The number of inherited E4 alleles is associated with both increased disease risk and decreased average age of onset compared with inheritance of the E2 or E3 alleles. The differences between the three ApoE isoforms are based on two amino acids that affect its structure and hence the interaction and binding of the protein with various lipids and beta-amyloid (AB). ApoE and AB can co-localize in the brain, and therefore their complementary roles in AD have been studied extensively. Circulating plasma and CSF ApoE levels were recently found to be potential biomarkers for AD.

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