A sweat test is the most reliable method for diagnosing cystic fibrosis (CF). It measures the amount of chloride (a component of salt) in sweat. People with CF have elevated chloride levels due to a genetic mutation that affects how salt moves in and out of cells. This test is especially important if a child shows symptoms of CF or has a positive newborn screening result.
If your child has been scheduled for a sweat test, it's important that they arrive prepared.
What happens during a sweat test?
Here's what to expect during a sweat test at Children's National.
Guidance for Testing Day
Where to Go
You are required to register at the front desk check-in upon arriving. Please bring identification with you. Please arrive 15 minutes before the appointment so that you can be registered. You will be sent to the second floor, where the Clinical Lab is located. When you arrive at the Lab, please tell the front desk staff that you are scheduled for a sweat test; this is important as the wait time will be shorter.
How to Prepare Your Child
- Important: Make sure that your child drinks enough fluids on the day before and the day of testing. Have them drink extra water or diluted fruit juices.
- If your child is not well hydrated, there is a chance that the test will not work and you will have to reschedule a second appointment. You will be given a bottle of water (if your child is old enough to drink) when you first check in at the Laboratory desk. If you are not given a bottle of water, please request one.
- Do not apply any creams or lotions on arms or legs of the patient on the day of testing.
- Continue to take all prescribed medications.
- There are no diet restrictions.
- If the child has a rash on their arms and legs on the day of testing, please reschedule the test.
- If the child was ill the day before the testing date, please reschedule the test. Often a child could be dehydrated, and this will affect the test collection.
- Bring books and toys that will entertain your child during the test – we ask that you remain in the Lab Lobby and not leave during the testing period.
- There is a consent form that the staff will provide to you upon arrival that requires signing before the test is performed.
