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
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
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 one of the defective
genes 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
CF carrier screening is recommended for all teen and adult females who are pregnant or are thinking about getting pregnant.1
If the test shows that you are a
carrier of cystic fibrosis (CF), your partner should also be tested.
If you had this screening test before, do not get tested again. Give your past results to your doctor.
What If I Am a Carrier?
Both parents must be
carriers of CF for a child to have the disease. If tests show that you are a carrier but your partner
is not a carrier of a 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.
This test does a good job of detecting whether a person is a carrier of the most common changed genes that can cause CF. The test is most accurate in Ashkenazi Jews and white people.2 This is partly because CF occurs most commonly in people of these ethnic groups. As with all tests, there is a small risk that you may be a CF carrier even when the test
results show that you are not a carrier.
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 of passing on to their children a disease that shortens life. Among whites, about 4 out of 100 are carriers of a defective CF gene.1 CF
is much less common in other racial and ethnic groups.
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
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.
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).
How this information was developed to help you make better health decisions.