Huntington's Disease Genetic Testing
If you are having genetic testing done for Huntington's disease, a sample of your blood will be taken. The DNA in this sample will be analyzed for the presence or absence of the Huntington disease mutation. In some cases, testing may also require a sample of DNA from a closely related affected relative, preferably a parent.
Genetic Testing for Huntington's Disease: An Overview
The discovery of the Huntington disease (HD) gene has led to the creation of a genetic test to make or confirm the diagnosis of the brain disorder. Huntington's disease is also known as Huntington disease, or HD.
Genetic testing has also led to screening for Huntington's disease. Screening consists of administering a test to people who do not have symptoms of Huntington's disease. If you think you may be at risk for this condition, you should talk with your healthcare provider about screening. There are many things to consider before deciding whether to be screened.
Using a blood sample, the Huntington's disease genetic test analyzes DNA for the genetic mutation by counting the number of CAG repeats in the specific gene. Individuals who do not have HD usually have 28 or fewer repeats; people with Huntington disease usually have 40 or more repeats (see Genetics of Huntington's Disease for more information).
The Process of Getting Tested
An individual who wishes to be tested should contact the nearest testing center. A list of such centers can be obtained from the Huntington Disease Society of America at 1-800-345-HDSA.
The testing process should include several components. Most testing programs include:
- A neurological examination
- Pretest counseling
The purpose of the neurological examination is to determine whether the person requesting the test is showing any clinical symptoms of Huntington's disease. It is important to remember that if an individual is showing even slight symptoms, he or she risks being diagnosed with the disease during the neurological examination, even before the genetic test.
During pretest counseling, the individual will learn about Huntington's disease, his or her own level of risk, and the testing procedure. The person will be told about the test's limitations, the accuracy of the test, and possible outcomes. He or she can then weigh the risks and benefits of testing and may even decide at that time against pursuing further testing.
If a person decides to be tested, a team of highly trained specialists will be involved, which may include:
- Genetic counselors
- Social workers
This team of professionals helps the at-risk person decide if testing is the right thing to do and carefully prepares the person for a negative, positive, or inconclusive test result.
Individuals who decide to continue the testing process should be accompanied to counseling sessions by a spouse, a friend, or a relative who is not at risk. Other interested family members may participate in the counseling sessions if the individual being tested so desires.
The genetic testing itself involves providing a small sample of blood that is screened in the laboratory for the presence or absence of the Huntington's disease mutation. Testing may also require a sample of DNA from a closely related affected relative, preferably a parent, for the purpose of confirming the diagnosis of Huntington's disease in the family. This is especially important if the family history for Huntington's disease is unclear or unusual in some way.