Prior to Testing

Confirming the diagnosis of HD in the family

It is important to make sure the diagnosis of HD is correct in the family. Often medical records on affected family members are requested. It is useful to perform the DNA blood test on an affected family member in order to confirm the presence of a CAG expansion. Individuals may also wish to discuss with a genetic counsellor or medical geneticist the advisability and implications of banking samples for possible future testing of other family members.

Education and counselling

Testing involves education and counselling about the implications of the test by someone with appropriate expertise. Testing may also involve neurological and/ psychiatric evaluation prior to the test being carried out.

For more information about each stage of the testing process please click on the diagram below:

The initial screening session usually involves a telephone conversation or office visit to give a brief overview of the testing process, what is involved, as well as collecting important family history and medical information from the individual considering predictive testing.

The genetic counseling session is usually with a genetic counsellor and/ or a medical geneticist. This appointment involves a personalised discussion about the inheritance and genetics of HD, as well as analysis of an individual’s family history. This session will include detailed discussions regarding reasons for pursuing testing, risks to family members and offspring, as well as other important considerations in the decision to undergo testing such as support, preparing for results, life insurance and possible discrimination.

A psychological/psychiatric evaluation is performed to assess an individual’s mental health status and emotional well-being prior to undergoing the potential distressing testing process. If significant psychological symptoms are identified, such as depression, changes in behaviour, or psychiatric illness a psychologist or psychiatrist should also be seen. In such cases it may be most appropriate to delay testing until these concerns are addressed. This process is an essential part of the testing process as it allows individuals who may need increased support to be identified and helped prior to completing the test.

A neurological examination may also be performed to assess whether an individual at risk for HD is exhibiting any signs or symptoms of a neurological disorder prior to undergoing testing and is actually ‘presymptomatic’. A person who is found to have subtle neurological changes may be at increased risk to receive a positive result or develop further symptoms. The neurological work-up can help provide the health care team with information regarding how an individual should be followed after the test results. For those who have a ‘negative’ neurological examination (i.e. exhibit no signs or symptoms of neurological changes) who then receive a positive genetic result (i.e. they have inherited the HD mutation), the neurological work-up may provide a helpful starting point for a long-term follow-up and care plan.

This is a general outline of the usual appointments and sessions provided during the predictive testing process, however this may vary due to the individual needs, as well as differences in predictive testing centres. The genetic test itself is usually performed via blood test, and the blood draw may occur during one of the initial appointments or at your doctor’s office. It is important to remember that you can stop, or pause, the predictive testing process at any time, and that you are under no obligation or pressure to complete the test or find out your results if you change your mind about undergoing testing.