Cystic Fibrosis (CF) Newborn Screening: Sweat Testing

Cystic Fibrosis Center

Cystic Fibrosis (CF) Newborn Screening: Sweat Testing

CF Information from Kids Health

For Parents

For Teens

For Kids

If a newborn screen test shows your baby might have cystic fibrosis (CF), a sweat test will make the final determination. The sweat test should be done in a Cystic Fibrosis Foundation accredited center to make sure that the test results are accurate.

What happens during a sweat test?

The sweat test measures the amount of salt in the sweat. No needles are used and the test will not hurt your baby. In the first part of the test, a chemical that causes sweating will be placed on a small area on both of your baby's arms. A weak electrical current is then passed through the skin by attaching small electrodes to the arm with an armband. This causes a tingling feeling much like when your arm is "asleep." A sweat collector containing tiny tubing is placed on the arm to collect the sweat. The sweat will then be taken to a lab, where the rest of the test will be completed.

What will the sweat test tell me?

Children and adults with cystic fibrosis have an increased amount of sodium and chloride (salt) in their sweat. In infants, sweat chloride results can be normal (meaning your baby does not have cystic fibrosis), intermediate (meaning that your baby could have CRMS: cystic fibrosis-related metabolic syndrome) or elevated sweat chloride (meaning that your baby has cystic fibrosis).

Preparing for the Sweat Test

Parents should not apply creams or lotions to the baby's skin 24 hours prior to the sweat test. There are no other special preparations before the test. There is no need to change the baby’s diet or other activity. All regular medications may be used and will have no effect on the test results.

Sweat Test Results

The lab will usually have the sweat test results ready for your doctor shortly after the sweat is collected. The clinic where the sweat test is done will tell you how they will inform you of the test results.

In a small number of cases, the test results fall into the intermediate range between not having cystic fibrosis and having cystic fibrosis. When this occurs, repeat sweat tests or blood tests may be done. These will only be done after talking to a doctor.