Genetic testing

Question

Dear ladies and gentlemen,
for our daughter, there had been the suspicion of CF, after the third test it could be excluded.
We are planning a child at the moment, can we get tested in advance that we can exclude, better say if our chances for a healthy baby are good?
Many thanks

Answer

Hello,
as seemingly in your daughter there was only the suspicion of CF and the diagnosis could in the end not been proven, a CFTR analysis of the parents is not indicated, unless in the family there is already a person known with CF.
In the white population every person in whose family there has not been a case of CF until now has a risk of about 1/25 to carry a CFTR-mutation, and a couple without familiar burden of CF has a general risk of about 1/2500, that its child will suffer from CF. In addition, all parents have a general risk of 3-5% that their child will be born with a malformation or illness. The other way round the chance of a healthy child is 95-97%.
There is no genetic testing (and also no other test) which guarantees, that a child will be born healthy. All available genetic tests can only answer one specific question more or less realibly. In case that in your family there is until now no known case of CF, an analysis of the entire CFTR-gene would have to be performed in order to lower the general risk of 1/2500, which implies a great effort and some costs. In case of a negative result the remaining risk of suffering from CF would however not be zero for the child (as the method has not a 100% detection rate), would however be lowered to 1/40 000 and would therefore be so to speak negligible. In case both parents coud be identified as carriers, a child would have a risk of 25% to suffer from CF, whereby, if wanted, a 100% prenatal diagnosis could be performed.
In case your daughter still shows symptoms, it would be important to find out the reason before a new pregnancy, in case to estimate resp. to exclude the risk for furhter children to suffer from the illness.
I hope to have answered your question sufficiently.
Yours sincerely,
Prof. Sabina Gallati

22.02.2011