Cystic Fibrosis Tests

How is Cystic Fibrosis diagnosed?

Cystic Fibrosis is increasingly being diagnosed through screening, but some babies and older children (and even adults) are diagnosed following unexplained illness.

There are three types of screening for Cystic Fibrosis: newborn screening, carrier testing and antenatal testing.

 Newborn Testing:

The test is a heel-prick to sample blood as part of the normal Guthrie test carried out on all children. The sooner cystic fibrosis is diagnosed, the sooner appropriate treatment can begin.

cystic fibrosis tests

heelprick test

Carrier Testing

A simple mouthwash test can be taken to tell if you are a carrier. This is important if a relative has CF or is a known carrier. It is very important to have the test if your partner is a known carrier.


children cystic fibrosis - examination

children cystic fibrosis - examination

Antenatal Testing

This test is used early in pregnancy to tell whether a baby has Cystic Fibrosis. It is usually offered to mothers who are at a high risk of having a child with Cystic Fibrosis.

Sweat Test:

After birth, the standard diagnostic test for cystic fibrosis is called the sweat test — an accurate, safe, and painless way to diagnose CF. In the sweat test, a small electric current is used to carry the chemical pilocarpine into the skin of the forearm. This stimulates sweat glands in the area to produce sweat. Over a period of 30 to 60 minutes, sweat is collected on filter paper or gauze and tested for chloride.

To diagnose CF, two sweat tests are generally performed in a lab accredited by the Cystic Fibrosis Foundation. A child must have a sweat chloride result of greater than 60 on two separate sweat tests to make the diagnosis of CF. Sweat test normal values for infants are lower.

Cystic fibrosis tests
sweat test
Cystic Fibrosis tests
chloride sweat test


Other Tests:

Several other tests are standard parts of the routine care used to monitor a child having CF.

  • Chest X-rays
  • Blood tests to evaluate nutritional status
  • Bacterial studies that confirm the growth of Pseudomonas aeruginosaStaphylococcus aureus, or Haemophilous influenzabacteria in the lungs .
  • Pulmonary function tests (PFTs) to measure the effects of CF on breathing (PFTs are done as soon as the child is old enough to be able to cooperate in the testing procedure)
    Cystic fibrosis tests
    Peak flow meter test of cystic fibrosis sufferer
    Cystic-Fibrosis chest-xray.

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