MedlinePlus Medical Encyclopedia: Sweat electrolytes

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Sweat electrolytes

Contents of this page:
Illustrations Alternative names Definition How the test is performed How to prepare for the test	How the test will feel Why the test is performed Normal Values What abnormal results mean

Illustrations

Sweat Test

Sweat test

Alternative names Return to top

Sweat test; Sweat chloride; Iontophoretic sweat test

Definition Return to top

This is a test that measures the level of chloride in sweat.

How the test is performed Return to top

A low-level electric current is applied to the test area. The positive electrode is covered by gauze and saturated with pilocarpine (a drug that stimulates sweating). The negative electrode is covered with gauze and saturated with bicarbonate solution.

A current is applied for 5 to 12 minutes, and a paper disk is then placed over the test site and covered with paraffin to obtain an airtight seal. After 1 hour, the disk is transferred to a weighing jar, then put in water to dissolve the salts. This solution is then analyzed for chloride.

How to prepare for the test Return to top

No special preparation is necessary.

How the test will feel Return to top

The test does not cause any discomfort.

Why the test is performed Return to top

Children with cystic fibrosis have increased sodium and chloride concentrations in their sweat. The test may be performed on infants to determine if early therapy is needed.

Normal Values Return to top

Normal values are as follows:

Sodium:
- Normal: less than 70 mEq/L
- Abnormal: greater than 90 mEq/L
- Equivocal: 70 to 90 mEq/L
Chloride:
- Normal: less than 50 mEq/L
- Abnormal: greater than 60 mEq/L
- Equivocal: 50 to 60 mEq/L

Note: mEq/L = milliequivalent per liter

What abnormal results mean Return to top

An abnormal test may indicate the presence of cystic fibrosis.

Update Date: 1/20/2004

Updated by: John Goldenring, M.D., M.P.H., Department of Pediatrics, Children's Hospital, San Diego, CA. Review provided by VeriMed Healthcare Network.

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