This test will be very accurate in almost all circumstances. Although the number of repeats is loosely correlated with the age of onset of HD, the association is not strong enough to be predictive of onset and should not be used clinically for this purpose. Presymptomatic testing of persons known to be at risk for HD, 2. Prenatal testing for HD, 3. The implementation of testing in each of these circumstances requires a different set of test and counselling guidelines.
Counseling strives to insure that the individual is making an informed choice.
A minimum of two pre-test counseling visits and a neurological examination are accepted as a standard. When a family history of HD is present, and a clinical neurological diagnosis cannot be made, the test is considered presymptomatic and appropriate counseling protocols should be adhered to. It is critical to recognize that when a clinical diagnosis of HD cannot be made, the genetic test will not confirm that equivocal symptoms represent the onset of the disease. The clinical neurological workup remains essential as the only means to recognize the onset of the disease. Past experience shows us that genetic testing in Huntington's disease can have a profound emotional impact on the individual and that individuals must be aware of the possible adverse consequences before testing.