Huntington’s is a genetic disease and a DNA test can be carried out which will usually tell you whether or not you have the faulty gene that causes it.
Although the test is available, this does not mean that you must or should have it. You need to consider very carefully whether the test is right for you.
Deciding to have the test for Huntington’s
- Only you can make the decision about whether you want to be tested, and you usually need to be over 18 before the test will be performed. Parents, partners and other family members may pressure you one way or the other, but it remains your decision.
- If you do decide to get tested, in addition to any emotional impact on you and your family, you also need to think about things like the effect of a positive result on other aspects of life such as life insurance and job opportunities. In certain occupations, such as the armed forces, it may be an obstacle to recruitment.
- If you have only recently discovered that you are at risk, be careful not to rush into making a decision about testing. Once you have been given your test results, you can’t change your mind about whether or not you wanted to know.
About the test
- Testing is only available at Regional Genetics Clinics, which are located throughout England and Wales. You can ask your GP to arrange an appointment for you.
- Going to a genetics clinic does not mean that you are obliged to take the test but it does give you the chance to talk over all the implications and any other concerns you may have. Each clinic follows an agreed counselling ‘protocol’; usually at least three sessions where you can talk over the implications of testing and any questions you may have, before you decide.
- You can withdraw from the testing process at any time.
- If you decide to have the test done you may have two separate blood samples taken (to double check the results). Your affected parent’s blood may also be tested to check the original diagnosis of Huntington’s disease. The DNA which is extracted from the blood is then analysed in a specialised laboratory.
- The clinic will want to allow time to ensure that a result is ready for you and you may need to wait around four to six weeks from your third counselling session for a result. Some people find waiting for the results very stressful. If you feel there is a particularly long delay, do ask the genetics clinic for the reason.
- According to national and international guidelines, follow-up counselling – after you have been given the test result – should be available. You can find out about this from your clinic.
Every person has two CAG repeats, one from the mother and one from the father. If one of the CAG repeats is above 40, this is classed as a positive result (full penetrance) and the person will go on to develop Huntington's disease. If both CAG repeats are under 26 then this is a negative result.
For a small minority though, the results are not quite as simple because they receive a result in the ‘grey area'. Reduced penetrance is in this grey area and this means that the person may or may not develop Huntington's disease. You can find out more about what this means here.
If you would like to talk to someone about testing you can speak to one of our Specialist Advisers for advice. You can also find out more about the testing process in our factsheet.