the discovery of the gene for HD in 1993, this question has loomed before thousands of people who are themselves at risk, or have friends or relatives at risk for Huntington's Disease.
There are no easy answers. Indeed, says Barbara Briscoe, a genetic counselor who runs the HD support group at UC Davis, there is no single answer. While the test is simple enough in technical terms, the issue of whether or not to undergo testing is fraught with complications.
The occurrence of HD correlated with
the presence of a mutation - in the form of repeated units of a triplet nucleotide sequence CAG - in a specific gene present in the upper portion of the
short arm of chromosome number 4.
"The average person has fewer than 29 CAG repetitions while individuals with HD consistently have upwards of 40 repeats in this gene," explained Briscoe. "The presence of 40 or more CAG repeats is a positive diagnosis - individuals will develop symptoms at some point in their life, if they live long enough."
But the test provides no more than a confirmation or negation of risk. There are no preventive measures against the disease. Furthermore, a positive diagnosis does not predict even exactly when the disease will strike or how severe it will be. In light of these considerations, many people decide against taking the test.
"Until there is a treatment or cure, I am firmly against predictive genetic testing," declared Judy Roberson. Judy's husband has the disease and their four children are therefore at risk for HD. "Once symptoms begin, I think it is a valid tool to confirm the diagnosis. But a positive diagnosis early in life may expose people to genetic discrimination and other problems.
"If you get tested and it goes in your medical record or on your insurance forms, you can risk being discriminated against for life, health and disability insurance and certain types of jobs,
even though you show no symptoms
of the disease," she said. "Also, it is important to be able to handle the knowledge that you have the genetic mutation. I recently learned of a 21-year old in Oregon who committed suicide two days after testing positive. I just don't think having this information too soon is helpul."
But not everyone agrees with this viewpoint.