Sweat test; Sweat chloride; Iontophoretic sweat test
How the Test is Performed
How to Prepare for the Test
No special steps are needed before this test.
How the Test will Feel
The test is not painful. Some people have a tingling feeling at the site of the electrode. This feeling may cause discomfort in small children.
Why the Test is Performed
A sweat chloride test result of less than or equal to 39 mmol/L in an infant over 6 months old probably means cystic fibrosis is very unlikely.
A result between 40 - 59 mmol/L does not give a clear diagnosis. Further testing is needed.
If the result is 60 mmol/L or greater, cystic fibrosis is present.
Note: mmol/L = millimole per liter
Normal value ranges may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results.
Some conditions, such as dehydration or swelling (edema) can affect the test results.
What Abnormal Results Mean
An abnormal test may mean that the child has cystic fibrosis.
Borowitz D, Robinson KA, Rosenfeld M, et al. Cystic Fibrosis Foundation evidence-based guidelines for management of infants with cystic fibrosis. J Pediatr. 2009;155(6 Suppl):S73-S93.
Egan M. Cystic fibrosis. In: Kliegman RM, Behrman RE, Jenson HB, Stanton BF, eds. Nelson Textbook of Pediatrics. 19th ed. Philadelphia, PA: Saunders Elsevier; 2011:chap 395.
Farrell PM, Rosenstein BJ, White TB, et al. Guidelines for diagnosis of cystic fibrosis in newborns through older adults: Cystic fibrosis consensus report. Journal of Pediatrics. Aug 2008;153(2).
Sameer Patel, MD, Assistant Professor of Pediatrics, Northwestern University, Feinberg School of Medicine, Chicago, IL. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Bethanne Black, and the A.D.A.M. Editorial team.