Sweat Chloride Test
(Cystic Fibrosis)

Medical Author: David Perlstein, MD, FAAP
Medical Author: Melissa Conrad Stöppler, MD

• What is the sweat chloride test?
• What is the aim of the sweat chloride test
• How is the sweat chloride test done?
• How long does the test take?
• What is done with the sweat?
• What are normal sweat chloride levels?
• What is the sweat chloride level in cystic fibrosis?
• What if the sweat chloride is intermediate (between normal and the usual cystic fibrosis levels)?
• Can a cystic fibrosis child have a normal sweat chloride level?
• Can the sweat chloride be high without having cystic fibrosis?

What is the sweat chloride test?

The sweat chloride test is a common and simple test used to evaluate a patient who is suspected of having cystic fibrosis (CF), the most common lethal genetic disease affecting Caucasians. Cystic fibrosis is often clinically suspected when there is poor growth during infancy or recurrent serious intestinal or respiratory diseases in a toddler or young child. The genetic defect in cystic fibrosis affects the way chloride moves in and out of cells, and sweat contains chloride in the form of sodium chloride (salt). Measurement of the chloride in sweat has been the standard method for diagnosing cystic fibrosis for over 40 years. Because cystic fibrosis is so common, many states include testing for the cystic fibrosis gene as part of the Newborn Screen; however, sweat testing is still required to confirm the diagnosis.

Suggested Reading by Our Doctors

• Cystic Fibrosis - Read about cystic fibrosis, a genetic disease of the mucus and sweat glands. Symptoms include bulky, foul smelling stools, abdominal pain, gas, malnutrition, and respiratory failure.
• Genetic Disease - Learn about genetic disease caused by abnormalities in an individual's genome. There are four types of genetic inheritance, single, multifactoral, chromosome abnormalities, and mitochondrial inheritance. Genetic testing is available for some genetic diseases.
• Genetic Counseling - Read about genetic counceling, what it is, who should receive genetic counceling, and resources such as how to find a genetic councelor for a particular disease or condition.

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