What Is Cystic Fibrosis?

Cystic fibrosis (CF) is an inherited disease caused by a change (mutation) in the cystic fibrosis transmembrane regulator (CFTR) gene. It is a chronic, progressive disease that causes mucus to become thick and sticky. The mucus builds up and clogs passages in many of the body's organs, but mostly in the lungs and the pancreas. In the lungs, the mucus can cause serious breathing problems and lung disease. In the pancreas, the mucus can cause digestive problems and malnutrition, which can lead to problems with growth and development.

What Causes CF?

Cystic fibrosis (CF) is a genetic disorder. A child must inherit two defective CF genes (one defective gene from each parent) to have the disease.

A person who has inherited only one defective CF gene is a carrier of CF and does not have the disease but can pass it on to his or her children. This person can also pass on carrier status.

• If only one parent is a carrier of a defective CF gene, the child will not have CF. But there is a 50% (1-in-2) chance that the child will be a CF carrier.
• If both parents are carriers, there is a 25% (1-in-4) chance that the child will have CF, and a 50% chance that the child will be a carrier.

What Is Carrier Screening?

Cystic fibrosis (CF) carrier screening is a blood test that determines if you are a carrier of the defective gene that causes CF. The test can help you determine if you and your partner have an increased chance of having a child born with CF.

Who Should Be Screened?

Genetic testing can help people find out if they may be carriers of cystic fibrosis (CF). This type of genetic testing allows parents to find out if they have an increased chance of having a child with CF. Anyone who is interested in knowing his or her carrier status can request the test, but the test can only be ordered by a doctor. Genetic counseling to help you understand the meaning and possible results of the test is recommended prior to genetic testing.

CF carrier screening is recommended for:¹

• Adults with a positive family history of CF.
• Partners of people with CF. If one partner has CF and the other partner has the defective CF gene, a child will have a 50% chance of having CF.
• Couples planning to have children.
• Pregnant women (and their partners) who seek prenatal care, regardless of family history.

What If I Am a Carrier?

If tests show that you are a carrier of cystic fibrosis (CF), your partner should also be tested. Both parents must be carriers of CF for a child to have the disease. If tests show that your partner is not a carrier of the CF gene, there is a very small chance that you will have a child with CF.

If you and your partner are both carriers of CF, there is a 1-in-4 (25%) chance that your child will have CF.

• If you are not already pregnant, you may wish to have genetic counseling to understand your risks and options if you decide to have children.
• If you are already pregnant, you may wish to have further testing (amniocentesis or chorionic villus sampling) to determine whether your baby has CF.

Is Screening Accurate?

The blood test can detect whether a person is a carrier of cystic fibrosis (CF) in about 9 out of 10 CF carriers.² This rate is not the same among all racial and ethnic groups. There is a small risk that you may be a CF carrier even when the test results are negative.

Should I Be Screened?

The decision to have cystic fibrosis (CF) carrier screening is a personal one. You may wish to be tested if you are concerned that you or your partner might be carriers of CF. This may be more likely if either of you has a family member with the disease.

Some people decide to be tested to help find out their risks if they choose to have children. Among whites, about 2 to 5 out of 100 are carriers of a defective CF gene.³ CF is much less common in other racial and ethnic groups.

Carrier testing is expensive. Another thing that may guide the decision to have testing is whether the cost of the test is covered by your insurance company.

You may decide to have carrier testing for CF if you are already pregnant. The test results may influence your decision about your pregnancy or help you make decisions about the care of your newborn child.

Why Not Be Screened?

There may be reasons you would choose not to have cystic fibrosis (CF) carrier testing.

• You think that your risk of being a carrier is low. This may be true if you are an African American or an Asian American. The incidence of CF is lower in these groups.
• You are already pregnant and the information obtained from testing will not affect your decision to continue your pregnancy. Remember, though, that CF test results can provide valuable information for the care of your unborn child.
• Carrier testing is expensive. You may decide not to have testing if your insurance does not pay for it.
• Testing does not identify all people who have a mutation in the CF gene. There is a small chance that you are a carrier even if the results are normal (negative).