Sweat Chloride Test (cont.)
What is the aim of the sweat chloride test?
The goal of this test is to painlessly stimulate the patient's skin to produce a large enough amount of sweat which may then be absorbed by a special filter paper and analyzed for the content of chloride in the sweat. Patients with cystic fibrosis produce larger quantities of sweat chloride than normal individuals.
How is the sweat chloride test done?
To produce the necessary volume of sweat, a technique called iontophoresis is employed. The technique requires the application of a tiny (painless) electrical current that medically stimulates maximum sweat production.
The patient's forearm is commonly used. However, in small infants, the back may also serve as an appropriate area to perform this procedure.
How long does the test take?
The sweat chloride test usually takes about one-half to one hour.
What is done with the sweat?
The sweat is collected on a specialized filter paper. After determining that enough sweat has been collected to ensure test reliability, the amount of chloride in the sweat is measured. This is considered a specialized test, and not all institutions have experience with the techniques, and poor collection techniques can result in false negative results.
What are normal sweat chloride levels?
The normal sweat chloride values are 10-35
milliequivalents per liter.
What is the sweat chloride level in cystic fibrosis?
Patients with cystic fibrosis usually have a sweat chloride value greater than 60 milliequivalents per liter.
What if the sweat chloride is intermediate (between normal and the usual cystic fibrosis levels)?
Intermediate values between 35 and 60 milliequivalents per liter may be seen in some cystic fibrosis patients (and in some normal children). In those cases, the sweat chloride test should be repeated in the very near future.
Next: Can a cystic fibrosis child have a normal sweat chloride level? »
- Cystic Fibrosis - Read about cystic fibrosis, a genetic disease of the mucus and sweat glands. Symptoms include bulky, foul smelling stools, abdominal pain, gas, malnutrition, and respiratory failure.
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