The sweat test is a quantitative measure of chloride in sweat, used in confirming a diagnosis of cystic fibrosis. It may be used in: patients with a phenotype suggestive of cystic fibrosis, patients with a family history of cystic fibrosis, confirmatory testing of a positive newborning screening result, suspicion of an atypical phenotype and monitoring of patients receiving treatment for Cystic Fibrosis.