The use of sweat osmolality in the diagnosis of cystic fibrosis

Abstract

Sweat osmolality determination with 7-10 microliter of sweat for the establishment of the diagnosis of cystic fibrosis (CF) was evaluated in 297 probands. In 12 out of 26 infants below 2 months of age and in 3 out of 271 older probands not enough sweat could be collected at the first attempt. A final diagnosis was established before the age of 2 months in 21 out of 26 infants. In 27 CF patients sweat osmolality was 285.86 +/- 41.25 mmol/kg (mean +/- SD), the mean value - 2 SD being 203.36 mmol/kg. In 266 control subjects sweat osmolality was 107.38 +/- 29.49 mmol/kg (mean +/- SD), the mean value + 2 SD being 166.36 mmol/kg. There was no overlap between CF patients and controls in each age group. The method is simple, rapid and reliable, and improves diagnostic possibilities especially in young infants. Sweat osmolality values above 180 mmol/kg should be repeated and checked for final confirmation or exclusion of the diagnosis of cystic fibrosis.