Both newborns and adults can be tested for the
changed (mutated) gene that causes cystic fibrosis. These tests include:
Newborn screening. Levels of
immunoreactive trypsinogen (IRT), a digestive enzyme, are measured from a blood
sample. High levels of IRT suggest cystic fibrosis. Some newborns may also have
genetic test for cystic fibrosis.
Genetic test for adults. These tests identify the most common defects in the
cystic fibrosis transmembrane regulator (CFTR) gene. Genetic testing can be
done during pregnancy through chorionic villus sampling or amniocentesis. The
test can also be done before pregnancy, to help couples determine whether
either or both of them carry a defective CFTR gene.
If both parents
carry the changed gene, there is a 25% (1-in-4) chance that their child will
have no genetic problem, a 25% chance that their child will have cystic
fibrosis, and a 50% (1-in-2) chance that their child will be a
If only one
parent is a carrier of the changed gene, the child will not have cystic
fibrosis. But there is a 50% chance that the child will be a carrier.
If you are interested in a genetic test for cystic
fibrosis, talk with your doctor about the test.
Genetic counseling can help you to understand your