[Sweat collection and osmometry in the diagnosis of cystic fibrosis: a new method]

Two methods of sweat testing (Gibson and Cooke's vs. sweat osmolality) for the diagnosis of cystic fibrosis were compared in 33 subjects (26 healthy subjects and 7 patients aged 23 days to 28 years). Sweat was collected with a "macroduct"-sweat collection-system, osmolality was measured with the Wescorvapor-pressure osmometry. In a further 18 subjects (13 healthy, 5 patients) electrolytes were determined from filter-paper and the Vescor-macroduct-system. The osmolality in sweat of healthy subjects and patients with CF differed significantly (p less than 0.001). In healthy subjects maximum osmolality was 198 mmol/kg (means 158 +/- 21.3 mmol/kg), in patients with CF 283.9 +/- 10.2 mmol/kg. Assessment of sweat osmolality is a highly reliable procedure for confirming the diagnosis of CF provided borderline-values between 180 and 220 mmol/kg are reevaluated with the conventional filter-paper assay.