Cystic Fibrosis Carrier Screening

What Is Cystic Fibrosis?

Cystic fibrosis (CF) is a common genetic disease that causes mucus in the body to become thick and sticky. The mucus builds up and causes problems in many of the body's organs, especially the lungs and the pancreas. People who have CF can have serious breathing problems and lung disease.

What Causes It?

CF is caused by a changed (mutated) gene that a child inherits from both parents. The changed gene causes problems with the way salt and water move in and out of the cells that make mucus. This causes the mucus to be thick and sticky. This glue-like mucus builds up and causes problems in many of the body's organs, especially the lungs and the pancreas.

Many people don't know they have the changed gene.

What Is Carrier Screening?

Cystic fibrosis (CF) carrier screening is a genetic test that shows if you are a carrier of the changed gene that causes CF. The test can help you find out if you and your partner have an increased chance of having a child born with CF.

Who Should Be Screened?

Anyone who is interested in knowing their cystic fibrosis (CF) carrier status can request the test. Genetic counselling to help you understand the meaning and possible results of the test is recommended prior to genetic testing.

Cystic Fibrosis Canada recommends carrier screening for family planning purposes for:^{footnote 1}

• People who have a family history of CF.
• People with a partner who has a family history of CF.
• People who have a medical condition that might be related to CF, such as male infertility.

If you are pregnant and have not had CF carrier screening, the Society of Obstetricians and Gynaecologists of Canada (SOGC) recommends testing for:^{footnote 2}

• People who have a positive family history of CF.
• People who have symptoms of CF.

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, don't get tested again. Give your past results to your doctor.

What If You Are a Carrier?

If tests show that you are a carrier of a genetic disease, your partner also should be tested. In most cases, both parents must be carriers for a child to get the disease.

• If you were tested before getting pregnant, genetic counselling can help you understand your risks and options if you decide to have children.
• If you are already pregnant, you may want to talk with your doctor about genetic counselling and screening your baby. Your baby may be tested using a sample of your blood or an amniocentesis or chorionic villus sampling.

Is Screening Accurate?

This test does a good job of detecting if a person is a carrier of the most common changes in the gene that can cause cystic fibrosis (CF). There are more than a thousand changes that can happen in this gene. If you have one of these rare changes, there is a small risk that you may still be a CF carrier even when the test results show that you are not a carrier.

Should You 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 before having children to help find out their risks of passing the CF gene on to their children. Among whites, the chances of being a carrier are higher than 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 child.

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 of African or Asian descent. 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 provincial health plan 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).