To diagnose cystic fibrosis, doctors may conduct several tests.

Newborn screening and diagnosis

Every state in the U.S. now routinely screens newborns for cystic fibrosis. Early diagnosis means treatment can begin immediately.

In one screening test, a blood sample is checked for higher than normal levels of a chemical (immunoreactive trypsinogen, or IRT) released by the pancreas. A newborn's IRT levels may be high because of premature birth or a stressful delivery. For that reason other tests may be needed to confirm a diagnosis of cystic fibrosis.

Genetic tests may be used in addition to checking the IRT levels to confirm the diagnosis. Doctors may also conduct genetic tests to test for specific defects on the gene responsible for cystic fibrosis.

To evaluate if an infant has cystic fibrosis, doctors may also conduct a sweat test when the infant is at least 2 weeks old. In a sweat test, doctors apply a sweat-producing chemical to a small area of skin. They then collect the sweat to test it and see if it's saltier than normal. Testing may be done at a center specializing in cystic fibrosis.

Testing of older children and adults

Cystic fibrosis tests may be recommended for older children and adults who weren't screened at birth. Your doctor may suggest genetic and sweat tests for cystic fibrosis if you have recurring bouts of inflamed pancreas (pancreatitis), nasal polyps, chronic sinus or lung infections, bronchiectasis, or male infertility.