genetic testing

Question

My partner was previously tested for cystic fibrosis. My partner doesn’t seem to have CF. Now we would like to have children but we wonder if (especially my partner) needs to have a genetic test done. His grandmother carries a CF gene. I have doubts because my partner was tested previously.

Answer

Thank you for this interesting question. Since CF runs in the family and since you are thinking about parenthood, it is important that both of you as a couple are being tested for the most frequent CFTR mutations. If your partner was tested previously for cystic fibrosis, without you knowing exactly which test was done, it is impossible to know the reliability of the previous screening. The best thing to do is to find the result of the previous test (screening for the most frequent CF mutations or sweat test?) and discuss the test result with your doctor so that he can guide you further.

In any case you need to know that if you nor your partner carry a CFTR mutation detected on routine screening, this only means that the chance that you will have a CF child is a lot lower than in the general population. This does not mean it is impossible. Indeed more than 1500 different CFTR mutations are at present known. Only the 35 most frequent mutations are being tested for routinely. If neither partner carries one of these 35 mutations, the risk of having a CF child is very low i.e. in the order of (1/250 x 1/250 x1/4) 1/250000. You can read much more about parenthood, genetics and carriership in the questions about genetics.
Kind regards
K. De Boeck

02.12.2010