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).
APOE Genotyping, Cardiovascular Disease
APOE Genotyping, Cardiovascular Disease
Also Known As
APOE Cardiac Risk
Formal Name
Apolipoprotein E Genotyping
This article was last reviewed
on
This article waslast modified
on July 24, 2018.
Were you looking instead for APOE genotyping ordered to evaluate for Alzheimer disease? If so, see APOE Genotyping, Alzheimer Disease.
At a Glance
Why Get Tested?
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
Accordion Title
Common Questions
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How is it used?
While APOE genotyping is mostly done in research settings, it can be used clinically to help in diagnosis and treatment of elevated lipid levels.
APOE testing may be used to help diagnose type III hyperlipoproteinemia (HPL III or familial dysbetalipoproteinemia) in a person with symptoms that suggest the disorder and to evaluate the potential for the condition in other family members. This is a rare inherited disorder that causes fatty, yellowish deposits on the skin called xanthomas, a high level of triglycerides in the blood, and atherosclerosis that develops at an early age.
APOE genotyping has potential to help guide lipid treatment. In cases of high cholesterol and triglyceride levels, statins are usually considered the treatment of choice to decrease the risk of developing cardiovascular disease (CVD). However, there is a wide variability in the response to these lipid-lowering drugs that is in part influenced by the APOE genotype. At present, the clinical utility of this type of information is yet to be totally understood.
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When is it ordered?
As a test to evaluate lipid metabolism or cardiovascular risk, APOE genotyping is ordered when someone has:
- Significantly elevated cholesterol and triglyceride levels that do not respond to dietary and exercise lifestyle changes
- Family members known to have abnormal APOE alleles and a healthcare practitioner wants to see if the person might be at a higher risk for early heart disease
- Yellowish skin lesions called xanthomas and the healthcare practitioner suspects type III hyperlipoproteinemia
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What does the test result mean?
APOE e3/e3 is the most common genotype. APOE e3 is associated with "normal" lipid metabolism, thus may not have any genetic impact on risk of developing cardiovascular disease.
APOE e4 (genotype e4/e4 or 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 significantly elevated levels of LDL-C ("bad cholesterol") and triglycerides when their diet is high in saturated fat.
People with the APOE e2/e2 alleles tend to have lower LDL-C levels but elevated triglycerides. APOE e2 is also associated with type III hyperlipoproteinemia/hyperlipidemia. People with APOE e2/e2 alleles are at a higher risk of premature vascular disease, but they may never develop disease. APOE genotyping adds additional information and, if symptoms are present, e2/e2 can help confirm type III hyperlipoproteinemia.
Most cases of apoE-influenced type III hyperlipoproteinemia occur in an autosomal recessive manner, meaning that individuals with an e2/e3 genotype may be carriers of disease but may not show signs of lipid dysfunction.
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Is there anything else I should know?
APOE genotyping is not available in every laboratory. If a healthcare practitioner recommends this test, the specimen will likely be sent to a reference laboratory and results may take longer to return than they would from a local laboratory.
Alterations in lipid concentrations do not lead directly to vascular disease or atherosclerosis. Other factors, such as obesity, diabetes, and hypothyroidism, also play a role in whether a person actually develops disease. Additionally, APOE genetic tests cannot detect all mutations that may cause type III hyperlipoproteinemia or other lipid-related diseases. Therefore, the absence of a mutation cannot rule out the possibility of disease or carrier status.
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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 healthcare practitioner additional information about a possible genetic cause for observed lipid abnormalities.
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Is there a reason to test for APOE genotype more than once?
