A sweat chloride test measures how much chloride, a part of salt, is in your child’s sweat. Too much chloride in the sweat is one sign of some diseases. It can mean that the body is not able to balance the amount of water it needs to function properly.
The test takes less than 2 hours. No needles will touch your child. The test does not hurt.
How to Prepare for the Test
- If your child is old enough, explain how the test done.
- Have your child drink lots of non-caffeinated liquids the day before and the morning of the test. Your child should be well-hydrated.
- Do not put any creams or lotions on their skin 24 hours before the test.
- Bring a sweatshirt, coat or a heavy blanket to keep them warm and to help them sweat during the test.
- Have something to entertain them during the test, like books, toys or games.
- Change your child’s diaper before the test, if needed, so they can stay bundled.
How the Test is Done
- A lab technician will clean an area on your child’s arm or leg and then strap on 2 electrodes. Beneath each electrode is a disk filled with a gel. The gel has a chemical in it that helps make the skin to sweat.
- The electrodes are hooked up to a machine. The machine will send a small amount of electricity (current) through the electrodes and gel for about 5 minutes. The current makes the skin sweat. Your child may feel warmth or tingling at the site but not an electric shock.
- The electrodes are then removed. The gel is cleaned off the arm or leg.
- The lab technician will tape a clear, collection disk that has coiled tubing in it over a spot where the electrodes were placed. It will stay there for about 30 minutes until enough sweat has been collected..
- Steps 1 through 4 will be repeated on the other arm or leg.
- After the second collection disk is in place, you and your child will go to the waiting room. Please keep your child bundled and warm the whole time the test is going on. They may move around quietly but should avoid activity that might loosen the collection disks.
- Do not leave the waiting room. If the child is not there when the collection disks need to be taken off, the test will have to be redone.
- The tubing in the collection disks will change color when they are full. Each will be snipped from their disk and the sweat put into separate test tubes for the lab. The collection disks are then taken off your child.
Occasionally, a child may react to the chemical gel and have a red mark or rash at the collection disk site. It will usually go away in a few hours. There is a very rare chance that the electrodes may burn your child’s skin. If the red mark or rash does not go away in a few hours or your child’s skin shows a burn, tell your child’s health care provider.
After the Test
- The tubes containing the sweat are sent to the lab. The results of the test will be sent to your child’s health care provider.
- If you have any questions, be sure to ask your child’s health care provider.
To make an appointment or get directions to the nearest Laboratory Service Center, please call Laboratory Services at (800) 934-6575 or visit NationwideChildrens.org/Lab.
HH-III-62 ©1983, Revised 2021, Nationwide Children’s Hospital