Carrier testing

Are you a carrier?

Once someone has been diagnosed with A-T in the UK, their DNA will be analysed to identify the two mutations they have. When this has been done, it is usually possible to test close relatives to tell whether or not they are carrying a mutation. This can be done because the laboratory staff know which mutations they are looking for.

However it is not yet possible to screen the general public or even partners of known carriers. This is because we do not know all the possible mutations which cause A-T. There may be some mutations or variations in the ‘spelling’ of the DNA which do not affect the functioning of the gene so it would be hard to distinguish these from A-T causing mutations. It is also a costly process.

Adults closely related to someone with A-T may wish to know if they are carriers, particularly if they are women, as being a carrier does bring an increased risk of breast cancer. However, in terms of having children there is little advantage in knowing whether or not you are a carrier, since you could not in any case screen your partner. The risk of potentially having affected children would depend on meeting another carrier – a 1 in 200 chance.

If you do wish to do this, you should first consult your GP. They can arrange either for you to see a genetic counsellor or for a blood test to be organised.

While it is possible for parents of children with A-T to have their other children tested to see if they are carriers, some may feel that this is something which it is better to leave to them to make a choice about when they are adults. If you are thinking of doing this, it is certainly advisable to talk the issue through with a genetic counsellor. In any case, your GP should be your first port of call.