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Chloride Sweat Testing for Cystic Fibrosis


Chloride sweat testing is used to help diagnose cystic fibrosis (CF), an inherited disorder that disrupts the normal function of epithelial cells found in the sweat glands and lining of passageways in the lungs, liver, pancreas, and digestive and reproductive systems. According to the Cystic Fibrosis Foundation, the sweat test is considered the gold standard for diagnosing cystic fibrosis. Sweat testing should be done at a CF Foundation-accredited care center.

People who have cystic fibrosis have increased amounts of chloride in their sweat. The sweat test measures the amount of chloride in the sweat, and can be done at any age. However, some infants may not make enough sweat to do the test. The test should be repeated in this case. During sweat testing, the skin is stimulated to produce enough sweat to be absorbed into a special collector. The sweat is then analyzed.

CLSI’s new document C34—Sweat Testing: Specimen Collection and Quantitative Chloride Analysis, 4th Edition describes methods for all aspects of sweat testing.

Vicky A. LeGrys, DrA, MT(ASCP), chairholder of C34 noted, “The primary audience for C34 includes laboratory and clinical personnel responsible for collecting, analyzing, reporting, and evaluating sweat test results. Sweat stimulation, collection, and the quantitative measurement of sweat chloride are described along with quality assurance and method validation.

Updates to the content include an expanded discussion of sweat testing infants following a positive newborn screening test; revised reference intervals for sweat chloride; and a greater emphasis on currently available collection devices and coulometric titration chloridometers.”


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