Cystic Fibrosis - Exams and Tests
Tests can help find out if a person has cystic fibrosis or has the changed gene that can be passed on to a child. Adults may want to get tested during a pregnancy or when they are planning for a pregnancy. People can be tested at any age to see if they have cystic fibrosis.
medical history and a
physical exam are often the first steps in diagnosing
cystic fibrosis, followed by screening or lab tests.
diagnosis of cystic fibrosis requires one of the
- Your child has early symptoms. These may include diarrhea that does not go away; large, greasy or very
smelly stools; constipation; not wanting to eat; or losing weight. To learn more, see Symptoms.
- A brother or sister who has cystic
- A positive
newborn screening test.
Also, there must be at least one of the following:
- A genetic test showing that a person inherited one or two defective cystic fibrosis transmembrane regulator (CFTR) genes. This testing can be done using blood or a sample from
the mother's womb before birth (chorionic villus sampling or
- Two positive
sweat tests on different dates. Sweat tests measure
the level of salt in sweat. People with cystic fibrosis have more than the
normal amount of salt in their sweat. If a genetic test detects two defective CFTR genes, then just one sweat test result may be all that is needed to confirm a diagnosis.
- An abnormal
nasal potential difference test. This test uses
electrodes on the lining of the nose to see how well salts flow into and out of
Monitoring cystic fibrosis
Certain tests can help your doctor monitor your child's cystic fibrosis.
These tests include:
- Lung function tests to find out how
healthy the lungs are by checking how well air moves into and out of the
throat culture or
sputum culture to see what kinds of bacteria are
causing any infections your child may have.
chest X-ray to take a picture of the chest, including
the heart and lungs.
CT scan to find any serious disease in the lungs,
pancreas, or other organs.
- Blood tests, such as glucose (blood
sugar) level and liver function. These tests are to see if there are any
complications of cystic fibrosis.
stool analysis to see how well your child is absorbing
and digesting fat and other nutrients.
arterial blood gas analysis to measure the levels of
oxygen and carbon dioxide in the blood. This test shows how well the lungs are