Cystic Fibrosis Carrier Testing

What is Cystic Fibrosis?

Cystic Fibrosis (CF) is one of the most common inherited diseases. It is most common among Caucasians, but can occur in other ethnic groups. About 1 in 3,300 newborns in the United States has CF.

CF causes abnormal secretion of mucus. People with CF may have chronic lung disease. They are more likely to have lung infections. They can also have problems with digestion. This causes diarrhea, poor growth, and malnutrition. Males with CF are usually infertile.

Is there a cure for CF?

There is no cure for CF. Some people have the disease more severely than others. The average lifespan is around 30 years.

Ethnicity	Carrier Risk	Detection Rate of CF Screening
Caucasian	1/29	90%
Ashkenazi Jewish	1/29	97%
Hispanic	1/46	57%
African American	1/65	69%
Asian American	1/90	30%

What causes CF?

Everyone is born with two copies of the gene that causes CF, one from their mother and one from their father. In most of us, both of these genes are normal.

Some people have one normal gene and one abnormal gene. They are called carriers. Carriers do not have CF.

CF is inherited as a recessive condition. A recessive condition means that both parents have the same abnormal gene. If a person is born with two abnormal CF genes, then he or she will have CF. They inherited one abnormal gene from each parent.

So, in order for a child to have CF, both the mother and father must be carriers. If both parents are carriers, there is a 25% chance that each of their children will have CF. But, that also means there is a 75% that each of their children will not have CF.

Could I be a carrier of CF?

People who have a family history of CF have a higher chance of being a carrier of CF. However, most CF carriers do not have a family history. Your chance of being a carrier also depends upon your ethnic background.

Because there are so many different possible changes in the CF gene, testing cannot detect all of them. Testing is done for the most common gene changes, and the detection rates also depend upon your ethnic background. In other words, it is easier to detect the CF gene in people of certain ethnic backgrounds. The detection rate is the percentage of carriers that will have a positive test. For example, look at the chart. If you are Caucasian, this means that if you are a carrier of CF, there is a 90% chance the test will detect it.

What if my carrier test is positive?

If your test is positive then you are a CF carrier. You do not have CF. The next step would be to test your partner. If he also has a positive test, there would be a 25% chance that each baby you have could have CF. If his test is negative, then the chance of having a baby with CF is greatly reduced. The chance is not zero because all gene changes cannot be detected.

If you are a CF carrier, then other members of your family may be as well. It would be important to share this information with relatives who may also wish to be tested.

What if my carrier test is negative?

A negative carrier test means that the chance that you carry CF is very low, but not zero. No further testing is recommended.

Can CF be diagnosed before birth?

Yes. If both parents are found to be carriers of CF they could choose prenatal testing to find out if the fetus has CF. This testing can be done during pregnancy by either chorionic villus sampling (CVS) or amniocentesis.

Should I be tested for CF?

Testing for CF is your choice. The American College of Obstetricians and Gynecologists and the American College of Medical Genetics recommend that all couples be offered screening during pregnancy or when planning a pregnancy. You may also wish to check with your insurance company to see if testing is covered.

What if I have more questions?

Questions can be addressed with your obstetrician/gynecologist or other healthcare provider Woman’s Hospital also has a certified genetic counselor who is available to discuss this information with you. She can be reached at 225-924-8754.