Apolipoprotein E Genotyping

Other names: Apo E Genotyping

Apolipoprotein E is one of the five main types of lipid protein; it is produced by the liver and brain. Apo E is responsible for transporting lipids around the body (from where they are produced to where they are stored) and transporting cholesterol from the organs to the liver, so that it can be excreted.

Why is the test used?

The Apo E test is not a common test; doctors usually use other types of test. However, the test may be useful under the following circumstances:

  • In the assessment of a patient who may be at risk of cardiovascular disease; this test can help doctors to measure the efficacy of treatment.
  • To diagnose Type III hyperlipoproteinemia (also known as familial dysbetalipoproteinemia)
  • To help with the diagnosis of late onset Alzheimer’s disease

The doctor will usually order this test when they suspect that a patient has inherited high cholesterol or triglyceride levels or when they notice symptoms of progressive dementia consistent with Alzheimer’s disease.

How is the test done?

The Apo E test is done using a blood sample, which is collected from a vein in the arm. The needle is inserted into a vein in the arm (usually on the inside of the elbow) and the sample is collected in a syringe. Once the sample has been collected, it can be bottled, labelled and sent away to the laboratory for analysis.

What do the test results mean?

Apo E genotyping examines which types of Apo E are present in the blood; there are three different forms, e2, e3 and e4. Every person inherits a combination of these forms and the e3/e3 is the most common genotype.

The presence of different combinations may indicate different health conditions; as follows:

  • E2/e2 alleles may mean there is a higher risk of vascular disease (however they may never actually develop the disease)
  • E4/e4 alleles may indicate a higher risk of atherosclerosis (this is when fatty deposits collect on the inside of the arteries)
  • E4 alleles may indicate a hugher risk of Alzheimer’s disease; however, this test should not be used to diagnose Alzheimer’s and doctors will order further tests in order to reach an accurate diagnosis

Specific Blood Tests

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