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Diagnosis of Cystic Fibrosis

How is cystic fibrosis diagnosed?

In addition to a complete medical history and physical exam, other tests for cystic fibrosis (CF) may include:

  • Sweat (chloride) test. This test measures the amount of chloride in the sweat. It's done 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 to your child. The sweat is collected onto a gauze pad and analyzed. Higher than normal amounts of chloride may suggest CF. The sweat test is not painful and usually causes only minor discomfort.

  • Genetic tests. Blood or cells taken from a cheek scraping can be tested for mutations in the CFTR gene. 

As part of the assessment of CF symptoms, your child may also have these tests:

  • Blood tests. Blood tests, including pancreatic function tests, can look at infection and to see which organs may be affected. 

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

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

  • Sputum cultures. This test is done on the material that is coughed up from the lungs and into the mouth. A sputum culture is often done to find out if an infection is present.

  • Stool evaluations. These are done to measure stool fat absorption.


Diagnosis of Cystic Fibrosis - WellSpan Health

Online Medical Reviewer: MMI board-certified, academically affiliated clinician
Online Medical Reviewer: Sather, Rita, RN
Last Review Date: 2014-10-01T00:00:00
Last Modified Date: 2014-10-03T00:00:00
Published Date: 2015-03-10T00:00:00
Last Review Date: 2007-03-30T00:00:00
© 2015 WellSpan Health. All Rights Reserved. This information is not intended as a substitute for professional medical care. Always follow your healthcare professional's instructions.

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