Cystic Fibrosis Home > Cystic Fibrosis Sweat Test

The sweat test for cystic fibrosis is the most useful test for making a diagnosis. The test measures the amount of salt in your sweat. It usually takes about 40 minutes. If you have a high level of salt, you may be diagnosed with cystic fibrosis.

What Is the Cystic Fibrosis Sweat Test?

In order to make a diagnosis of cystic fibrosis (CF), your doctor will need to:
  • Obtain a detailed medical and family history
  • Perform a thorough physical examination
  • Order tests to ensure an accurate diagnosis.
One of the tests that your doctor will use is the cystic fibrosis sweat test.

How Does the Sweat Test for Cystic Fibrosis Work?

The sweat test is the most useful test for determining if a person has cystic fibrosis. This test measures the amount of salt in your sweat. To perform it, your doctor will follow this process:
  • First, your doctor will rub a small amount of a chemical called pilocarpine on your arm or leg.
  • Then your doctor will attach an electrode to this spot. The electrode provides a mild electric current that produces sweat. This may cause tingling or a feeling of warmth.
  • Then your doctor will cover the area with a gauze pad or filter paper and wrap it in plastic.
  • After 30 to 40 minutes, your doctor will remove the plastic so that the sweat that collected on the pad or paper can be analyzed.
The cystic fibrosis sweat test is usually performed twice. In general, high levels of salt would indicate that you have the disease.

(Click Cystic Fibrosis Diagnosis to learn more about how this condition is diagnosed.)
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Last reviewed by: Arthur Schoenstadt, MD
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