Cystic Fibrosis Diagnosis

The Norton Children’s Cystic Fibrosis Program offers cystic fibrosis (CF) care that treats the whole child and family. Families often receive a CF diagnosis for their child soon after birth. Learn more about how CF is diagnosed.

How Is CF Diagnosed?

Today, most children with CF are diagnosed through a newborn screening.

Older children, those born before the use of CF newborn screenings or those who had a negative newborn screening still can be diagnosed with CF. If a physician is concerned about a child’s growth or if a child has many sinus or lung issues, they may be referred to a Cystic Fibrosis Foundation-accredited care center for evaluation and diagnostic testing, including sweat testing and genetic testing.

Cystic Fibrosis Newborn Screening

All 50 states screen newborns for CF within the first few days after birth. A few drops of blood from a heel prick are placed on a special card and tested for elevated levels of immunoreactive trypsinogen (IRT). High levels of IRT do not always mean the baby has CF. In Kentucky and Indiana, a baby with an elevated IRT automatically will have genetic testing.

The diagnosis needs to be confirmed with further testing, such as a sweat test, which is considered the gold standard for diagnosing CF. Sweat testing is performed in infants at least 2 weeks old. The family will be referred to a Cystic Fibrosis Foundation-accredited care center for sweat testing and interpretation of results.

A positive newborn screen does not always indicate the child has CF but can mean the child is a carrier, having one abnormal gene and a normal sweat test. People who are carriers shouldn’t have symptoms of CF but could have children with CF.

What Do Sweat Test Scores Mean?

A sweat chloride value of 60 millimoles per liter or higher is consistent with CF. A value between 30 and 59 millimoles per liter is inconclusive and may require further testing. A value less than 30 millimoles per liter is considered normal.

Can You Test for CF While Pregnant?

CF can be diagnosed in an unborn baby during pregnancy using one of two tests:

  • Chorionic villus sampling (also called CVS): A small piece of the placenta is obtained to check for genetic abnormalities in the fetus; usually performed at 10 to 12 weeks’ gestation
  • Amniocentesis: A sample of amniotic fluid from around the baby in the uterus is tested for genetic conditions, including CF; performed at 15 to 20 weeks’ gestation

The American College of Obstetricians and Gynecologists recommends that all people who are considering pregnancy or are currently pregnant be offered a CF gene carrier screening.

Can Parents be Tested to See if They are CF Gene Carriers?

Adults planning to have children can be tested to determine if they are carriers for the condition. Genetic counseling is available for parents who are found to be carriers.

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