Protocol - Sweat Chloride Test

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Quantitative pilocarpine iontophoresis is the procedure also known as the sweat chloride test. It involves stimulation of sweat, collection of sweat onto gauze or filter paper, measurement of the weight or volume of sweat collected, and analyses to determine the sweat chloride concentration.

Specific Instructions

The Cystic Fibrosis Foundation (CFF) accredits cystic fibrosis centers to perform sweat testing. The CFF strongly recommends that any laboratory that performs sweat testing be accredited by their organization.

The Rare Genetic Conditions Working Group indicates that normally this test is performed on infants and young children and may be less accurate when performed on adults. Also the Working Group acknowledges, sweat testing is exclusively performed in relation to cystic fibrosis.




The following description is a summary. See Clinical and Laboratory Standards Institute (CLSI) document C34-A2 for the full protocol. The test should be performed at a CFF accredited laboratory. In addition, the CFF has also provided testing guidelines (LeGrys et al., 2007) that should be followed.

  • Pilocarpine is applied to gauze or filter paper.
  • Electrodes are attached to the gauze or filter paper.
  • The electrodes are attached to the newborn’s lower arm or upper leg for about 5 minutes. Sweat collection should not occur longer than 30 minutes.
  • Collect a minimum of 75 mg of sweat.
  • Quantitatively analyze the sweat for chloride concentration by coulometric titration using a chloridometer, or using the Schales and Schales mercuric nitrate procedure or an automated analyzer that has been validated against the other methods.
  • It is recommended but not required that the test be repeated on the newborn.

Reference values

Sweat chloride concentrations < 40 mmol/L are negative; 40 to 60 mmol/L are borderline/intermediate; > 60 mmol/L are positive.

Personnel and Training Required

Trained laboratory staff at a Cystic Fibrosis Foundation-accredited laboratory.

Equipment Needs

Iontophoresis equipment (battery powered)

Requirement CategoryRequired
Major equipment Yes
Specialized training Yes
Specialized requirements for biospecimen collection No
Average time of greater than 15 minutes in an unaffected individual No
Mode of Administration



Infant, Toddler, Child, Adolescent, Adult, Senior, Pregnancy


Infants 48 hours old to adults

Selection Rationale

The sweat chloride test is considered the gold standard for the diagnosis of cystic fibrosis.



caDSR Form PhenX PX221701 - Sweat Chloride Test 6200813 caDSR Form
Derived Variables


Process and Review

This section will be completed when reviewed by an Expert Review Panel.

Protocol Name from Source

LeGrys, V.A., et al. Diagnostic sweat testing: The Cystic Fibrosis Foundation guidelines. J Pediatr, 2007


CLSI. Sweat Testing: Sample Collection and Quantitative Chloride Analysis; Approved Guideline-Third Edition. CLSI document C34-A3. Wayne, PA: Clinical and Laboratory Standards Institute; 2009.

LeGrys, V. A., Yankaskas, J. R., Quittell, L. M., Marshall, B. C., & Mogayzel, P. J., Jr. (2007). Diagnostic sweat testing: The Cystic Fibrosis Foundation guidelines. Journal of Pediatrics, 151(1), 85-89.

General References

Farrell, P. M., Rosenstein, B. J., White, T. B., Accurso, F. J., Castellani, C., Cutting, G. R., Durie, P. R., Legrys, V. A., Massie, J., Parad, R. B., Rock, M. J., & Campbell, P. W.; Cystic Fibrosis Foundation. (2008). Guidelines for diagnosis of cystic fibrosis in newborns through older adults: Cystic Fibrosis Foundation consensus report. Journal of Pediatrics, 153(2), S4-S14.

Mishra, A., Greaves, R., & Massie, J. (2005). The relevance of sweat testing for the diagnosis of cystic fibrosis in the genomic era. Clinical Biochemist Reviews, 26, 135-53.

Protocol ID


Export Variables
Variable Name Variable IDVariable DescriptiondbGaP Mapping
PX221701010000 Negative Sweat test - Cystic Fibrosis N/A
PX221701020000 Borderline Sweat test - Cystic Fibrosis N/A
PX221701030000 Positive Sweat test - Cystic Fibrosis N/A
Rare Genetic Conditions
Measure Name

Sweat Chloride Test

Release Date

April 30, 2015


An assay to determine if a person has cystic fibrosis.


The sweat chloride test is the gold standard test used to diagnose cystic fibrosis. It is recommended after a newborn screens positive for cystic fibrosis or when a patient of any age is suspected of having cystic fibrosis.


Cystic fibrosis, sweat chloride, sweat test, Cystic Fibrosis Foundation, CFF, quantitative pilocarpine iontophoresis, newborn screening

Measure Protocols
Protocol ID Protocol Name
221701 Sweat Chloride Test

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