If cystic fibrosis is suspected, a genetic test may be done to confirm the results of an unclear or positive sweat test. This blood test detects changes in the genetic material (DNA) that causes cystic fibrosis.

A genetic test may also be done to screen people who want to know whether they are likely carriers of cystic fibrosis, or what their chances are of having a child who has cystic fibrosis. Anyone who is interested in knowing his or her status can request the test, but a doctor must order it and the test is fairly expensive. Genetic counseling is recommended before having a genetic test.

Some states offer genetic testing for the cystic fibrosis gene. The National Institutes of Health (NIH) recommend testing for:¹

• Adults who have a positive family history of cystic fibrosis. They may be a carrier of the defect in the cystic fibrosis gene.
• Partners of people who have cystic fibrosis. If the partner also has the defective cystic fibrosis gene, a child will have a 50% (1 in 2) chance of having cystic fibrosis.
• Couples who are currently planning to become pregnant.
• Pregnant women (and their partners) who seek prenatal care, regardless of family history.

A genetic test for cystic fibrosis also can be done before birth using chorionic villus sampling (CVS) or amniocentesis.