At a glance
Also known as
Apo E genotyping
Why get tested?
To help confirm a diagnosis of Type III (also known as dysbetalipoproteinaemia); occasionally to help confirm a diagnosis of late onset Alzheimer's disease (AD) in a symptomatic adult
When to get tested?
If your doctor suspects that your high cholesterol and triglyceride levels may be due to a genetically inherited disorder, or if you have xanthomas (yellowish raised patches) on your skin
A blood sample drawn from a vein in your arm
Confused about genetics?
See our Genetics Information
What is being tested?
Apolipoprotein (Apo) E is produced under the direction of the APOE gene, is produced primarily in the liver and brain and has two primary metabolic roles:
- The transport of lipids from where they are made or absorbed to the tissues where they are stored.
- The transport of cholesterol and other lipids from the body's organs to the liver for excretion. ApoE also plays a role in lipoprotein metabolism. It helps clear very low-density lipoprotein (VLDL) and chylomicrons, the large lipoproteins that are responsible for the initial transport of dietary lipids to the liver, from the bloodstream.
This test looks at a person's to determine what combination of APOE forms (genotype) are present. The APOE gene exists in three different forms (alleles) – e2, e3, and e4 – with e3 being the most common allele, found in 60 per cent of the general population. Everyone inherits two APOE genes, one from each parent, that is some combination of these three forms, e.g. e2/e2, e2/e4, e3/e4.
APOE e3/e3 is the most common genotype. APOE e4 (e4/e4 and e4/e3) is found in 25 per cent of the population and is associated with higher LDL-C ("bad cholesterol") and an increased risk of atherosclerosis.
People with the APOE e2 allele tend to have lower LDL-C levels but elevated triglycerides. APOE e2/e2 is also associated with type III hyperlipoproteinaemia/hyperlipidaemia (HPL III or familial dysbetalipoproteinaemia), a rare inherited disorder that causes fatty yellowish deposits on the skin called xanthomas, increased triglycerides in the blood, and atherosclerosis. Less than 20 per cent of people with e2/e2 develop type III, and usually requires other factors such as obesity or diabetes in order to develop.
How is the sample collected for testing?
A blood sample is obtained by inserting a needle into a vein in your arm.