“Screening for CF is part of newborn screening in every state in the U.S. A positive newborn screening is not a diagnosis of CF. But it does mean more testing is done.

The first test done to try to diagnose CF is a sweat chloride test. This measures the amount of salt in your child’s sweat.

Testing for the CF gene can be done from a small blood sample. Or it can be done from a cheek swab. For this, a brush is rubbed against the inside of your cheek. This is done to get cells for testing. Labs generally test for the 20 or so most common mutations.

Not all of the genetic errors that cause CF have been found.”

Stanford Children’s Health/Lucile Packard Children’s Hospital Stanford