At a Glance
Why Get Tested?
To help confirm a diagnosis of Type III hyperlipoproteinaemia (also known as dysbetalipoproteinaemia), to evaluate a possible genetic cause of atherosclerosis, or 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 concentrations may be due to a genetically inherited disorder, or if you have xanthomas (yellowish raised patches) on your skin; also sometimes used if you have progressive symptoms of dementia and your doctor wants to investigate a possible cause of Alzheimer's Disease
A blood sample taken from a vein in your arm
Test Preparation Needed?
No test preparation is needed
The Test Sample
What is being tested?
The test looks at a patient's DNA to determine what combination of Apo E gene alleles (copies) he or she has. The ApoE gene exists in three different forms – e2, e3, and e4 – with e3 being the most common form and considered to be 'neutral'. Everyone has a pair of ApoE genes that is some combination of these three, for example e3/e3, e2/e2, e2/e4 etc.
Apolipoprotein (Apo) E is made in the liver and brain and helps transport lipids (fats) from one place to another thus helping to clear dietary fats, such as triglycerides, from the blood.
The e2 form of ApoE is less able to clear lipids from the blood compared to the other forms. This means that if someone has an e2/e2 combination, they may clear dietary fat from their body at a slower rate and be at a higher risk for early vascular disease because of the increased likelihood that the fats will be deposited in the blood vessel walls. It is not a straightforward diagnosis, however, as other factors, such as obesity, diabetes, and hypothyroidism, may play a role in whether a patient actually develops disease.
The Apo e4 allele has been shown to be associated with an increased risk of late onset Alzheimer's Disease (developing after the age of 65). While one copy of e4 constitutes a risk (e2/e4 or e3/e4) and two copies of e4 (e4/e4) indicate a greater risk of developing AD, the actual amount of risk involved has not been fully established.
How is the sample collected for testing?
A blood sample is obtained by inserting a needle into a vein in your arm.
NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.
Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.
Is any test preparation needed to ensure the quality of the sample?
No test preparation is needed.
Ask a Laboratory Scientist
NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.