Predictive/Pre-Symptomatic Testing

The gene responsible for Huntington disease was identified in 1993, making it possible for people at risk of HD to have genetic testing through the predictive testing program available to people aged 18 years and over.

There will, in the majority of cases, be one of two outcomes:

  1. Carrying the HD gene (gene positive)
  2. Not carrying the HD gene (gene negative)
However, in approximately 2% of results, an ‘at risk’ person may be told their result falls in the “grey zone” - that is, the person may never exhibit symptoms, or only very mildly, or at a much later age. There remains the risk though that their child (or children) can inherit the disease in its more usual pattern.

Deciding whether to take the test is a personal choice and everyone will feel differently about whether they want to know or not. The decision is one which makes huge demands on the thoughts and emotions of many who know that they are at risk of the condition.  

In Victoria, the Predictive Testing Program is operated by Genetic Health Services Victoria (formerly the Victorian Clinical Genetics Services) and is available at the Royal Children’s Hospital.

The person requesting testing must:

  • Be at risk of HD, with the diagnosis of HD having been confirmed in a parent (or grandparent)
  • Be 18 years of age or older. In rare circumstances, a younger teenager who demonstrates capacity to give informed consent may enter discussions with a view to testing
  • Be free from severe depression or psychotic disorder
  • Agree to participate in counselling sessions, including result giving (disclosure) and post test follow up
  • Preferably be accompanied by a partner or supportive friend - not another at risk person
  • Provide details of a local medical practitioner with whom participation in the program has been discussed. This doctor is asked to provide additional support if necessary.

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