Cystic Fibrosis Home > Cystic Fibrosis Diagnosis

In order for your doctor to make a diagnosis of cystic fibrosis, he or she will need to obtain a detailed medical and family history, perform a thorough physical examination, and order tests. The test that is most useful for making a diagnosis is the sweat test. This measures the amount of salt in your sweat; high levels generally indicate cystic fibrosis.

How Is Cystic Fibrosis Diagnosed?

When considering a diagnosis of cystic fibrosis (CF), your doctor will need to do the following:
  • Obtain a detailed medical and family history
  • Perform a thorough physical examination
  • Order tests to ensure an accurate diagnosis.

Diagnosing Cystic Fibrosis Using the Sweat Test

The sweat test is the most useful test for making a cystic fibrosis diagnosis. 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 test is usually performed twice. High levels of salt would mean that you have cystic fibrosis.
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Last reviewed by: Arthur Schoenstadt, MD
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