Sweat chloride concentration is considered as a biomarker for diagnosis of cystic fibrosis (CF). This application compares the results obtained with the sweat test using the WynSep capillary electrophoresis (CE) method and coulometric measurement (Chlorochek chloridometer, CC) of sweat chloride in subjects with suspected CF. The Wyn-CE exhibits an excellent correlation with the quantitative coulometric test, and can be used in the diagnosis of CF for newborn screening or  in children with a light weight.