What Is a Sweat Chloride Test?
A sweat chloride test, also called a sweat test, is a test done to find out if a child has cystic fibrosis (CF).
Children have this test done when they had an abnormal newborn screen, or because they are having symptoms that are sometimes seen in children who have cystic fibrosis.
What Is Cystic Fibrosis?
Cystic fibrosis is a genetic condition in children and adults. About one out of every 3,000 people has CF. It most often affects the lungs and digestive system. Children with CF may have chronic lung infections or problems digesting their food.
Signs and Symptoms
It is important to know that many children have some of these symptoms but they do not have CF:
- Chronic cough
- Frequent lung infections
- Poor weight gain
- Nasal polyps
- Wheezing
- Salty skin
- Frequent, bulky bowel movements
How Is a Sweat Test Done?
The sweat test is a simple test that takes about one hour. It is done by placing a solution on both forearms, or less often, the lower legs, and stimulating the skin to sweat with a small electrical current. The sweat is then collected on a small piece of gauze. The amount of salt in the sweat is then measured to determine the results. People with CF have saltier sweat than people who do not have CF.
Your child may feel a tingling in their arms or legs during the test, but the test is not painful.
Preparing Your Child for the Sweat Test
- Make sure that your child drinks lots of fluids the night before the test. Being well hydrated helps children sweat enough so that the test does not need to be repeated.
- Your child should not be on iodide or bromide. It interferes with the sweat chloride test. This does not include iodide found in vitamins or salt.
- Bring a jacket, sweater, blanket and hat for your child to wear during the test to ensure they are warm and sweat during the test.
- Do not use soap or lotion on your child's arms or legs for 24 hours before the test. Bathing or showering with water only is OK.
- Babies can be bottle fed or breastfeed during the test.
