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Apolipoprotein E Genotyping Test

Last updated July 23, 2019

Approved by: Maulik P. Purohit MD, MPH

The Apolipoprotein E Genotyping Test is a blood test that determines the allele of Apo E they contain. It is used as a risk factor for coronary artery disease and is also used to detect genetic abnormalities.

What are the other Names for this Test? (Equivalent Terms)

  • Apo E Genotyping
  • APOE Cardiac Risk
  • APOE Genotyping

What is Apolipoprotein E Genotyping Test? (Background Information)

  • Apolipoprotein E or Apo E, is a type of protein necessary for the regulation of fat metabolism
  • Apolipoproteins are protein components of lipoproteins (“apo-“ meaning detached). Lipoproteins are carriers of cholesterol and fats. They are necessary because cholesterol and fats are not soluble in blood, and would otherwise coagulate and clog blood vessels
  • There are different kinds of lipoproteins, depending on the ratio of protein to fat:
    • Very-low density lipoproteins (VLDL) and chylomicrons contain high amounts of fat per protein
    • High-density lipoproteins (HDL) contain less fat per protein. They transport fat and cholesterol from the body back to the liver for metabolism. Thus, they are called “good”
    • Low-density lipoproteins (LDL) transport fat and cholesterol from the liver to the rest of the body. Thus, they are called “bad”
  • Lipoproteins contain apolipoproteins - the type of apolipoprotein contained by a lipoprotein determines, where the lipoprotein will go. This is because, cells at the destination recognize lipoproteins by the apolipoproteins they contain
  • Apolipoprotein E is contained by chylomicrons and intermediate-density lipoproteins (IDL)
  • The instructions for production of the Apo E protein reside on the APOE gene. There are 3 variants, or alleles, of APOE - e2, e3, and e4. These give instructions for their own variant of Apo E, which are Apo E-2, Apo E-3, and Apo E-4, respectively
  • Apo E-2 is less effective at being recognized than the other Apo E variants. Thus, an individual with the e2 allele is more likely to display higher blood fat levels, than individuals with other alleles
  • The Apolipoprotein E Genotyping Test is a blood test that determines the allele of Apo E they contain. It is used as a risk factor for coronary artery disease and is also used to detect genetic abnormalities

What are the Clinical Indications for performing the Apolipoprotein E Genotyping Test?

Following are the clinical indications for performing the Apolipoprotein E Genotyping Test:

  • Evaluating the risk for coronary artery disease (CAD), which is marked by:
    • Chest pain or discomfort
    • Shortness of breath
    • Fatigue
    • Jaw pain
    • Family history of cardiovascular disease
  • Yellow skin lesions (xanthomas)

How is the Specimen Collected for Apolipoprotein E Genotyping Test?

Following is the specimen collection process for Apolipoprotein E Genotyping Test:

Sample required: Blood

Process: Insertion of a needle into an arm vein.

Preparation required: No special preparation is needed prior to the test.

What is the Significance of the Apolipoprotein E Genotyping Test Result?

The significance of Apolipoprotein E Genotyping Test is explained:

  • The presence of e2 may indicate a predisposition to coronary artery disease
  • Additionally, abnormalities in the APOE gene may mean congenital hyperlipoproteinemia, or HPL type III

The laboratory test results are NOT to be interpreted as results of a "stand-alone" test. The test results have to be interpreted after correlating with suitable clinical findings and additional supplemental tests/information. Your healthcare providers will explain the meaning of your tests results, based on the overall clinical scenario.

Additional and Relevant Useful Information:

  • The Apolipoprotein E Genotyping Test is often performed alongside other tests, such as a triglycerides test. These tests may require fasting for 12 hours
  • The percentage of the population that possesses e2, e3, and e4, are 10%, 63%, and 25%, respectively
  • Apolipoprotein E genotyping has revealed a loose correlation to atherosclerosis and Alzheimer’s disease

Certain medications that you may be currently taking may influence the outcome of the test. Hence, it is important to inform your healthcare provider, the complete list of medications (including any herbal supplements) you are currently taking. This will help the healthcare provider interpret your test results more accurately and avoid unnecessary chances of a misdiagnosis.

References and Information Sources used for the Article:

Reviewed and Approved by a member of the DoveMed Editorial Board
First uploaded: July 19, 2014
Last updated: July 23, 2019