APOE Genotyping, Cardiovascular Disease
- Also Known As:
- APOE Cardiac Risk
- Formal Name:
- Apolipoprotein E Genotyping

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At a Glance
Why Get Tested?
APOE genotype tests are most often done as part of research protocols to help understand the role of genetic factors in cardiovascular disease. However, the testing is sometimes used in clinical settings to help confirm a diagnosis of type III hyperlipoproteinemia (also known as familial dysbetalipoproteinemia).
Were you looking instead for APOE genotyping used in Alzheimer disease?
When To Get Tested?
When your healthcare provider suspects that you have an inherited component to your high cholesterol and triglyceride levels or if you have yellowish lesions called xanthomas on your skin
Sample Required?
A blood sample drawn from a vein in your arm
Test Preparation Needed?
None
What is being tested?
Apolipoprotein E (Apo E) is a protein that helps transport lipids (fats and cholesterol) in the blood. It is recognized by specific cell surface receptors that allow it to deliver lipids to cells for use or storage and to deliver excess lipids to the liver for excretion.
The ApoE protein has three genetic forms that have slightly different compositions. They are called ApoE2, ApoE3, and ApoE 4. ApoE3 is the most common form. Compared to ApoeE3, ApoE2 is poorly recognized by cell surface receptors whereas ApoE4 binds more tightly to those receptors. People with ApoE2 tend to have higher amounts of lipids in their blood since delivery from blood to cells is impaired by poor binding of ApoE2 to receptors.
Three different genes (termed alleles) are designated as e2, e3, and e4 and code respectively for ApoE2, ApoE3, and ApoE4. Each person inherits one allele from each parent. A person who has the same allele from each parent is termed homozygous: e2/e2 or e3/e3 or e4/e4. One who has different alleles is termed heterozygous: e2/e3 or e2/e4 or e3/e4.
The APOE genotype test evaluates a person’s DNA to determine what APOE forms (alleles) are present. APOE e3/e3 is the most common genotype (seen in well over half of the population) and is considered “neutral.” Risks of disease are made relative to the e3/e3 population. APOE e4 (as e4/e4 and e4/e3) is found in nearly a quarter of the population and is associated with an increased risk of atherosclerosis. People with these genotypes could be predisposed to a significantly elevated level of LDL-C (“bad cholesterol”) and triglycerides when their diet is high in saturated fat. The various APOE allele frequencies differ between ethnic populations.
People with the APOE e2 allele tend to have lower LDL-C levels but elevated triglycerides. APOE e2 is also associated with type III hyperlipoproteinemia/hyperlipidemia (HPL III or familial dysbetalipoproteinemia), a rare inherited disorder that causes fatty yellowish deposits on the skin called xanthomas, increased triglycerides in the blood, and atherosclerosis that develops at an early age. Importantly, while a large majority of patients with type III hyperlipoproteinemia are homozygous for the e2 allele (e2/e2), less than 10% of people with the e2/e2 genotype develop type III hyperlipoproteinemia/hyperlipidemia.
Common Questions
View Sources
Sources Used in Current Review
2017 review performed by Allison B. Chambliss, PhD, DABCC, FACB, Scientific Director, LAC+USC Medical Center Core Laboratory.
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