Genetic Testing

The HD gene was identified in 1993. Prior to the availability of this DNA blood test, confirmation of HD was made on the basis of linkage analysis. There are two HD genetic testing protocols: confirmatory testing and presymptomatic testing. Both protocols result in DNA analysis for the HD gene expansion.

Confirmatory Testing

Confirmatory testing is indicated when a person has a positive family history and exhibits signs and symptoms of Huntington's disease. DNA analysis for the HD gene expansion is available only in specialized molecular genetics laboratories. Processing of samples can take 2-4 weeks. This type of testing is used when the clinical condition is clear and the diagnosis is being confirmed.

Presymptomatic Testing

Individuals at risk for Huntington's disease have the option to test their DNA for the gene expansion. There are several presymptomatic testing sites in the United States. The Huntington's Disease Society of America maintains a list of testing sites. People considering testing are encouraged to contact an HDSA testing site which provides a neurologic evaluation and counseling as part of the testing protocol. Testing is a very individual decision and should be discussed with professionals experienced in genetic testing for Huntington's disease. More information on presymptomatic testing is available here. Residents of Northern California can contact us at testing@hdteam.org for information on the nearest testing site.