Alzheimer’s Genetic Test

General Description

The Alzheimer’s genetic test consists of analyzing the APOE gene, which is associated with the development of this condition. Of the three variants of this gene (E2, E3, and E4), the E4 allele is the one that confers an increased risk of developing Alzheimer’s disease. It is estimated that approximately 40% of affected individuals carry at least one copy of the E4 allele.

It is important to note that carrying one copy of the E4 variant does not mean that the disease will necessarily develop; it only indicates a probability, since many other factors contribute to the onset of Alzheimer’s. In fact, it is estimated that only about 1% of cases correspond to a purely genetic familial disease. However, being aware of this genetic predisposition allows individuals to take preventive measures and modify lifestyle habits to reduce the likelihood of disease progression.

When is it indicated?

The Alzheimer’s genetic test is recommended in the following situations:

• Family history of Alzheimer’s disease.
• Family history of dementia or cognitive impairment.

How is it performed?

To perform the test, a blood sample is collected, from which the patient’s DNA is extracted. The extraction follows the same procedure as routine blood analyses:

• The arm is kept extended and the fist clenched.
• An elastic tourniquet is placed above the elbow.
• The area is disinfected, and a needle is inserted into one of the veins in the inner part of the elbow.
• The tourniquet is removed and the hand is relaxed.
• Blood is collected in a sterile tube with a lavender cap, which contains an anticoagulant (EDTA) to keep the sample in liquid form for a longer period.

In the laboratory, the blood is treated with sodium sulfate to access the interior of the molecules that contain DNA (usually proteins), and with isopropanol or ethanol to precipitate the deoxyribonucleic acid strand, as DNA is not soluble in alcohol. Finally, the sample is centrifuged to separate the DNA.

To study the APOE gene specifically, the DNA segment where it is located is isolated. The most commonly used techniques today for this genetic study of Alzheimer’s disease are exome sequencing and next-generation sequencing (NGS). In both methods, the patient’s DNA fragment is compared with a reference sample using advanced technological equipment that enables a fast and reliable analysis to obtain structured data.

Risks

The Alzheimer’s genetic test does not pose any health risks.

What to expect from an Alzheimer’s genetic test

On the day of the blood sample collection, it is recommended to wear clothing that allows easy access to the arm. It is normal to feel slight discomfort when the needle is inserted into the vein, but it is usually brief. To prevent bruising, pressure should be applied to the puncture site for a few minutes. Once the process is completed, the patient may resume normal daily activities.

Test results typically take about 20 days from the time of sample collection. If the results are positive, the physician will determine the next steps and any additional tests that may be required.

Specialties that request the Alzheimer’s genetic test

Genetics specialists perform this analysis, which is generally requested by Neurology departments.