Childen's Hospital Boston 300 Longwood Avenue
Boston, MA 02115
(617) 355-6000
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My Child Has:
Sweat Test
Programs that perform this test
Center for Healthy Infant Lung Development (CHILD)   Cystic Fibrosis Center  
What is it?
The Sweat Test is a quick and easy test used to diagnose cystic fibrosis. Developed at Children's Hospital Boston, the Sweat Test has gained national acceptance as a reliable indicator of cystic fibrosis. At Children's, we perform more than 1,250 sweat tests each year.

The purpose of a sweat test is to make an area of the skin sweat enough so that the sweat can be collected, and the salt (sodium and chloride) concentration in the sweat can be determined. The test takes about 40-45 minutes from start to finish.

What happens in during the test?
  • Preparation:
    We start by putting two gauze pads on each forearm. The pad closest to the wrist has a mild chemical in it and is used to stimulate or activate the sweat glands. It feels like water.

  • Stimulation:
    We then attach electrodes to the pads and run a small current through them. This part of the test lasts 5 to 10 minutes and may not cause any sensation, or may cause a mild tingling. The test is not painful.

  • Collection:
    After 5 to 10 minutes of stimulation, we wipe the sites with water, dry the arms, and put pre-weighed gauze on the sites that were stimulated. The gauze is then covered with plastic wrap, secured with tape, and left in place for 25 minutes. During this time, the child can sit in the hallway or go for a walk and is allowed to eat if desired.

  • Analysis:
    After the waiting period, the gauze pads are removed and analyzed for salt content. Although the results are not ready immediately, they will be called into your primary care physician's office on the day of the test.
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