The sweat test, considered the gold standard for diagnosing cystic fibrosis, is a simple and painless procedure. During this test, a small, watch-like special device is attached to the child's arm. The device gently stimulates sweat production, and the amount of salt (chloride) in the collected sweat samples is analyzed. A diagnosis of cystic fibrosis can be made when the salt level in the sweat exceeds normal reference values.