Sweat Chloride Test
Also written as: SCT — Sweat Chloride Test
The gold-standard diagnostic test for cystic fibrosis, measuring the concentration of chloride ions in sweat collected by pilocarpine iontophoresis.
Full Definition
The sweat chloride test (SCT), also called the sweat test, quantifies chloride concentration in sweat induced by pilocarpine iontophoresis. A sweat chloride value ≥ 60 mmol/L is diagnostic for cystic fibrosis in children; values between 30–59 mmol/L are intermediate and require further evaluation including CFTR mutation analysis. The test is standardized by the Clinical and Laboratory Standards Institute (CLSI) and requires minimum sweat collection quantities for valid results. Editors should ensure units are expressed as mmol/L (not mEq/L or mg/dL) and that the procedure is not referred to simply as a 'chloride test', which may be confused with serum electrolyte testing.
Usage
Usage note: Express results in mmol/L. Do not abbreviate to 'chloride test' in clinical documents to avoid confusion with serum electrolyte panels.
In Context
- "A sweat chloride test result of 72 mmol/L confirmed the clinical suspicion of cystic fibrosis in the four-week-old infant referred after a positive newborn screen." — Outpatient clinic letter
- "The report listed sweat chloride units as 'mEq/L'; the editor standardized these to 'mmol/L' per current CLSI guidelines." — Laboratory report editorial note