Conductivity determined by a new sweat analyzer compared with chloride concentrations for the diagnosis of cystic fibrosis

Objectives The aim of the study was to determine if a new conductivity measuring sweat test system (Nanoduct) could reliably identify patients with cystic fibrosis (CF) and differentiate them from healthy subjects. Study design On the same day and in the same patient, the new system was tested in comparison with the Macroduct sweat collection system measuring chloride concentration and osmolality. Results Subjects (n = 111) 3 weeks to 60 years of age were investigated. Three children had no sweat production, and in 14 children, only conductivity could be measured. in the remaining 94 subjects, the new system identified all patients with classic CF (mean conductivity, 115 mmol/L; range, 92 to 137) and differentiated them from healthy subjects (mean conductivity, 36 mmol/L; range, 17 to 59) within a mean time of 20 minutes. Conclusions Measuring sweat conductivity using the new test system reliably differentiated between patients with and those without CF. This suggests that the new system could be used as a diagnostic test in addition to its suggested screening value.