Genetic Carrier Testing

Overview

Medical technology now can provide information about the future health of individuals. Using genetic information, tests can be offered to determine if a person might have a child that may have certain diseases or health care needs, such as cystic fibrosis (CF).

A genetic test is most often given to expectant parents. It can be used to confirm a diagnosis of CF, but the test to diagnose CF is the sweat test. For someone to have the disease, two copies of the defective CF gene must be inherited--one from each parent. A carrier has only one copy of the CF gene mutation and, thus, does not have the disease or symptoms.

What is genetic carrier testing for CF?

Genetic carrier testing can be used to tell if a person carries one or more mutations of the CF gene and how many copies of each mutation. The test looks at a person's DNA (genetic material), which is taken from cells in a blood sample or from cells that are gently scraped from inside the mouth.

Although only about one of every 3,000 Caucasian newborns has CF, there are more than 1,000 known mutations of the gene that causes CF. Current tests look for the most common mutations.

The mutations screened by the test vary according to a person's race or ethnic group, or by the occurrence of CF already in the family. More than 10 million Americans, including one in 29 Caucasian Americans, are carriers of one mutation of the CF gene. In other races or ethnicities, one in 46 Hispanic Americans, one in 65 African Americans and one in 90 Asian Americans carry a mutation of the CF gene.

If you have a relative with CF or who is known to carry a mutation of the CF gene, your chances of carrying a mutation are greater because of your family's history. If you are pregnant or planning to have a child, you should discuss this test and the results with a health professional who is knowledgeable about genetic testing, such as a genetic counselor.

• What is CF?
• Should I get genetic carrier testing for CF?
• How does someone inherit a mutation of the CF gene?
• What does a positive genetic carrier test for CF mean?
• If I have one copy of the defective CF gene, can my children have CF?
• How does CF "appear" when no one in my family has ever had the disease?
• Do certain types of the defective CF gene make the disease more mild or severe?
• Can genetic testing diagnose CF?
• Can a fetus be tested for CF?
• Is there hope for a healthy future for people with CF?

What is CF?

Cystic fibrosis is a genetic disease and causes the body to make a thick, sticky mucus that clogs the lungs and other organs, such as the pancreas. In the lungs, this mucus leads to chronic infections and progressive loss of lung function. The mucus obstructs the pancreas, preventing digestive enzymes from reaching the intestines to help break down and absorb food, and it can also block the bile duct in the liver, eventually causing permanent damage in approximately six percent of people with CF.