Cystic Fibrosis - Exams and Tests
Tests to diagnose
cystic fibrosis can be done at any time-before
pregnancy, during pregnancy, in childhood, or in adulthood.
Genetic tests for couples who are planning a pregnancy
or who are expecting a baby can help determine whether either person is a
carrier of the changed (mutated)
gene that causes cystic fibrosis. Babies can be
screened for cystic fibrosis shortly after they are born, especially if they
have symptoms or are at risk of inheriting the changed gene. Most people who
have cystic fibrosis have signs of it when they are children.
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 one or more of the common
- A brother or sister who has cystic
- A positive
newborn screening test. For this test, a small amount
of the baby's blood is tested to see how much of a digestive enzyme called
immunoreactive trypsinogen (IRT) is present. Babies with cystic fibrosis have
more IRT than normal.
Also, there must be at least one of the following:
- 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.
- A positive
genetic test for the genetic defect that is known to
cause cystic fibrosis. Genetic testing can be done using blood or a sample from
the mother's womb before birth (chorionic villus sampling or
- 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 identify any serious disease in the lungs,
pancreas, or other organs.
- Blood tests, such as glucose (blood
sugar) level and liver function, 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 to see how well the lungs are