Tests and diagnosis

By Mayo Clinic Staff

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 the 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 may be high because of premature birth or a stressful delivery. For that reason other tests are needed to confirm a diagnosis of cystic fibrosis:

  • Sweat test. A sweat-producing chemical is applied to a small area of skin. The collected sweat is then tested to see if it's saltier than normal.
  • Genetic testing. DNA samples from blood or saliva can be checked for specific defects on the gene responsible for cystic fibrosis.

The sweat test is usually done when the infant is a month old, to ensure the sample is large enough to be analyzed. The sweat test can determine if the infant carries the cystic fibrosis gene or has the condition. Testing should 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.

Testing after diagnosis

If you have cystic fibrosis, you will need regular tests to help manage the condition:

  • Imaging tests. Damage to your lungs or intestines can be monitored with X-rays, CT scans and MRI.
  • Lung function tests. These tests measure the size of your lungs, how much air you can breathe in and out, how fast you can breathe in and out, and how well your lungs deliver oxygen to your blood.
  • Sputum culture. Your spit (sputum) is analyzed for bacteria.
  • Organ function tests. Blood tests can measure the health of your pancreas and liver. Children with cystic fibrosis should be regularly tested for diabetes after age 10.
June 13, 2012