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Sweat Chloride Test

Sweat Chloride Test Helps Diagnose Cystic Fibrosis

Also known as: Sweat electrolytes, sweat test, iontophoretic sweat test

Your doctor may order a sweat chloride test if your child displays symptoms of cystic fibrosis, such as frequent respiratory infections and coughing, chronic diarrhea and malnutrition. The test also may be ordered as a follow-up test to confirm a diagnosis of cystic fibrosis.
 
Preparation and Procedure

Sweat chloride tests are performed by appointment only. Be sure to call the lab to schedule a time for the test.

  • On the day of the appointment, dress your child in loose-fitting clothing to allow easy access to his or her arms and legs.
  • At the lab, a sweat sample will be collected using a special procedure known as pilocarpine iontophoresis. A technician will wash a patch of skin on your child’s leg or forearm and then attach an electrode containing a sweat-stimulating liquid (pilocarpine). The electrode will generate a weak electrical current to stimulate the child’s sweat glands for 5-10 minutes. This procedure is painless; at most the child will feel a light tingling or tickling.
  • The electrode will be removed and the test area will be washed and dried. You may notice redness or blister-like welts on your child’s skin. (This is a normal reaction to the pilocarpine, and it will go away in 2-3 hours.)
  • The test area will be covered by a piece of plastic-like material called parafilm. This will protect the area and allow sweat to accumulate for 30 minutes.

The test area will then be touched with a wand that will register the amount of chloride in the sweat.

Time Required

The entire test takes approximately 90 minutes. Results from the test are typically sent to your doctor within days; be assured, however, that any critical results are communicated immediately. Your doctor will discuss the results with you once he or she has reviewed them.

Michigan law requires that a valid order signed by an authorized person be presented before any laboratory test or procedure can be conducted. Authorized persons are defined as physicians, physician assistants, or nurse practitioners. These professionals are legally responsible for interpreting the results of tests based on their knowledge of the individual patient.