Sweat electrolytes

Alternative names:

iontophoretic sweat test; sweat chloride; sweat test

How the test is performed:

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 min 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:

No special preparation is necessary.

How the test will feel:

The test does not cause any discomfort.

Why the test is performed:

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.