A sweat test measures the amount of chloride present in the sweat. In the first part of the test, a colorless, odorless chemical (pilocarpine) and a little electrical stimulation is applied to a small area of an arm or leg to encourage the sweat glands to produce sweat. A person may feel tingling in the area, or a feeling of warmth.
Once the sweat is collected on a piece of filter paper or gauze or in a plastic coil. The sweat sample is sent to a hospital laboratory to measure how much chloride is in the sweat. The sweat test usually takes about an hour, but it may take longer.
People with CF have more chloride (a component of salt) in their sweat than people who do not have CF.For a child who has CF, the sweat chloride test results will be positive (showing a high chloride level) shortly after birth. A baby has to sweat enough to do the test. Full-term babies usually produce enough sweat by 2 weeks of age.
Other Diagnostic Procedures