Testing for Cystic Fibrosis

How can you know for sure if you or your child has cystic fibrosis? If someone in your family has the disease, could you pass it down to your children?

There are several ways to help answer these important questions.

Sweat Test — If a person shows symptoms of CF or if a baby has a positive newborn screen for CF, a doctor may order a sweat test. This simple, painless test is the best way to diagnose CF. It measures the concentration of salt in a person’s sweat. A high salt level indicates CF.

Sweat tests should be done at a Cystic Fibrosis Foundation-accredited care center where strict guidelines help ensure accurate results.

Click here to learn more about the sweat test.

Newborn Screening — Newborns screened for cystic fibrosis can benefit from early diagnosis and treatment, which can:

  • Improve growth;
  • Help keep lungs healthy;
  • Reduce hospital stays; and
  • Add years to life.

While newborn screening is not a definitive diagnostic test for cystic fibrosis, it may lead to tests that can rule out or confirm a CF diagnosis. All states in the U.S. screen newborns for cystic fibrosis.

Click here to learn more about newborn screening.

Genetic Carrier Testing — More than 10 million Americans are symptomless carriers of the defective CF gene. This blood test can help detect carriers, who could pass CF onto their children. To have cystic fibrosis, a child must inherit one copy of the defective CF gene from each parent.

Each time two carriers of the CF gene have a child, the chances are:

  • 25% (1 in 4) the child will have CF;
  • 50% (1 in 2) the child will carry the CF gene but not have CF; and
  • 25% (1 in 4) the child will not carry the gene and not have CF

CF Punnett Square

Click here to learn more about genetic carrier testing.

For more information:

Updated 12/17/10