Diagnosis of Cystic Fibrosis

How is cystic fibrosis diagnosed?

In addition to a complete medical history and physical examination, diagnostic procedures for cystic fibrosis may include the following:

• Sweat (chloride) test--a test to measure the amount of chloride in the sweat. The test is performed by placing a solution on the forearm (or the thigh if the child is too small) and attaching electrodes. The skin is stimulated to sweat with a mild electric current, which does not cause pain or harm your child. The sweat is collected onto a gauze pad and analyzed. Higher than normal amounts of chloride may suggest cystic fibrosis. The sweat test is not painful and usually causes minor discomfort.

• Genetic tests--blood or cheek scraping cells can be tested for mutations in the CFTR gene. 

• Blood tests--blood tests, including pancreatic function tests, can assess infection, and involvement of certain organs. 

• Chest X-rays--a diagnostic test which uses invisible electromagnetic energy beams to produce images of internal tissues, bones, and organs onto film.

• Pulmonary function tests--diagnostic tests that help to measure the lungs' ability to exchange oxygen and carbon dioxide appropriately. The tests are usually performed with special machines that a child must breathe into.

• Sputum cultures--a diagnostic test performed on the material that is coughed up from the lungs and into the mouth. A sputum culture is often performed to determine if an infection is present.

• Stool evaluations--to measure stool fat absorption.