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Tests and Services

Sweat Test and Special Needs Phlebotomy

Sweat Test

Children's National Medical Center is the only local laboratory that performs sweat testing for diagnosing cystic fibrosis. Children’s highly-trained laboratory staff performs more than 1,000 tests annually.

Sweat tests are used to diagnose cystic fibrosis because children with the condition have more sodium and chloride in their sweat than children without cystic fibrosis. A sweat test is a painless, noninvasive procedure that takes 30 minutes to an hour.

Preparing for a sweat test
  • Children may eat, drink and exercise normally.
  • Children can take medications on their usual schedule.
  • Parents and guardians should plan to stay with their child during the test or consider asking a friend or family member to do so.
  • Bring a favorite book or toy to help pass the time while the test is done. The laboratory waiting room has distractions, such as television and interactive toys.
Sweat test procedure
  • A sweat sample is collected using a special sweat stimulation procedure.
  • A tiny amount of a sweat-stimulating liquid is applied to a small patch of skin on the arm or leg.
  • An electrode is then placed over the patch of skin and a weak electrical current stimulates the area, sometimes resulting in a painless tingling or warm sensation.
  • After several minutes, the area is cleaned and sweat is collected for approximately thirty minutes.
  • The sweat obtained is then analyzed for chloride.
  • Parents and guardians may help with the test and stay with their child during the test.
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Special Needs Phlebotomy

Children with special needs and a variety of medical issues may require numerous laboratory tests. The laboratory team strives to provide a peaceful atmosphere for testing by:
  • Providing a quiet, private area for the blood drawing procedure.
  • Using alternate forms of communication other than speech, such as physical gestures.
  • Working with the caregiver to gain the child’s attention.
  • Explaining directions carefully, simply and slowly.
  • Repeating directions aloud to help the patient remember them.
  • Accepting and provide positive feedback.
  • Taking time to assist a child with transitions.
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Sweat Test and Special Needs Phlebotomy - Departments & Programs - Children's National Medical Center