What is Cystic Fibrosis?
Cystic Fibrosis (CF) is one of the most common inherited diseases, affecting about 1 in 3300 people in the United States. It is most common in Caucasians, but does occur in other ethnic backgrounds.
CF causes the body to produce thick mucus leading to pneumonia, diarrhea, poor growth and infertility. Intelligence is normal. While severely affected individuals die in childhood, the average life span is around thirty years; and may improve as scientists search for better treatments.
Why Are Some Babies Born With CF?
If both parents are carriers of a CF gene, each of their children has a 25% chance of having the disease and a 75% chance of not having it. These chances are the same for each pregnancy, regardless of sex. Carriers are not themselves affected by the disease.
The diagram below shows the different genetic combinations that can be passed to children when both parents are carriers, each having one normal gene (N) and one CF gene (CF).
Who Are Carriers and How Can They Find Out?
If there is no one in your family with CF, your risk for being a CF carrier is shown in the following table along with the detection rates of the CF carrier test (the numbers vary slightly among different laboratories):
If someone in your family has CF, then no matter what your ethnic background, your chance of being a carrier increases depending on how closely related you are to the person with CF. Your specific risk can be determined by a doctor or by a genetic counselor.
CF carrier testing requires a small sample of blood. The results are usually ready in 10-14 days.
What If Your Test Results Show You Are as CF Carrier?
• If your test shows you have one CF gene, then you are a CF carrier. This result does not affect your own health.
• If one member of the couple is a CF carrier and the other is not, then the risk is less than 1 in 1000 (0.1%) that any child of theirs would have CF.
• If both parents are CF carriers, each pregnancy has a risk of 1 in 4 (25%) that the child will be affected.
• If only one member of the couple has been tested and is found to be a carrier, the partner should be tested as soon as possible.
The information from the carrier test may help in your family planning, as well as alert family members to the possible need for CF testing. You may wish to consult with your doctor or a genetic counselor for further discussion of what the results mean for you and your family.
What If Your Test Results Do Not Show A CF Gene?
CF testing cannot find all carriers. The test takes into account your ethnic background and any family history of CF. If your test results do not show a CF gene, the chance that you are a CF carrier is low, but never zero.
Is There Prenatal Testing for CF?
Yes. The same CF test that is done on blood samples can also be done on amniotic fluid. The accuracy of the prenatal test is greater when both parents have been tested for CF. The accuracy also depends on knowing that the man tested is in fact the biological father.
Prenatal testing for CF is appropriate when:
Both parents of the pregnancy are CF carriers.
Ultrasound (sonogram) of the fetus shows signs of CF, such as blocked intestines. In this case, blood samples from both parents should be sent for testing at the same time as the amniocentesis sample.
There is any other at-risk situation. Talk to your doctor or to a genetic counselor.
Will Insurance Cover the Cost of the CF Carrier Test?
Health plans and insurance coverage may vary. It is best to ask your plan representative before having the carrier test.
For Further Questions…
This webpage contains the general information regarding carrier testing for CF. However, you may wish to obtain professional genetic counseling prior to having the test.
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