Apolipoprotein E (Apo E) genotyping
What is analysed?
Apolipoprotein E (Apo E) is a protein that helps transport lipids (fat) and cholesterol.
There are several isoforms (variants) of the Apo E protein, but three major ones - Apo E2, Apo E3, and Apo E4 - are most commonly found in humans. Everyone possesses a pair of Apo E genes that forms different combinations, for example E3/E3, E2/E4 etc.
Apo E genotyping is an analysis that examines specific variations in the APOE gene.
What does the result mean?
The result indicates which isoform of the APOE gene a patient carries.
Specific and different combinations of isoforms are associated with varying risks for cardiovascular and neurodegenerative conditions.
Why conduct the analysis?
Apo E genotyping is conducted to help diagnose Type III hyperlipoproteinaemia, a rare genetic disorder that affects lipid metabolism, leading to abnormal elevations in cholesterol and triglyceride levels in the blood.
When to conduct the analysis?
Apo E genotyping is conducted in various clinical scenarios:
- When high cholesterol and triglyceride concentrations are suspected to be caused by a genetic disorder.
- When types of xanthomas (raised yellow patches) on the skin are observed.
What sample is required?
A blood sample is required. The blood is taken from a vein, usually in the arm.
Is any prior preparation necessary?
No prior preparation is required.
How is it performed?
The sample is sent to a laboratory, where it is analysed using molecular techniques such as polymerase chain reaction (PCR) and DNA sequencing to identify the specific isoform of the Apo E gene.
What does having altered values mean?
| APOE genotype | Interpretation |
|---|---|
| APO E2/E2 | Increased risk for cardiovascular and Alzheimer's diseases |
| APO E2/E3 | Moderate risk for cardiovascular and Alzheimer's diseases |
| APO E2/E4 | Increased risk for cardiovascular and Alzheimer's diseases |
| APO E3/E3 | Balanced profile, average risk for cardiovascular and Alzheimer's diseases |
| APO E3/E4 | Moderate risk for cardiovascular and Alzheimer's diseases |
| APO E4/E4 | Increased risk for cardiovascular and Alzheimer's diseases |
- Apo E2: Apo E2 is less able to remove lipids from the bloodstream compared to the other isoforms and is associated with a higher risk for early cardiovascular disease.
- Apo E3: Apo E3 is considered to be ‘neutral’, representing a common and balanced profile with average risks for cardiovascular and neurodegenerative conditions.
- Apo E4: Apo E4 is associated with an increased risk of cardiovascular diseases and a higher risk of developing Alzheimer's disease.