[Comparison of conductivity with sodium determination in the same sweat sample]

OBJECTIVE: To correlate sweat conductivity by Wescor with quantitative sodium determination in the same sample. METHODS: We analyzed 206 sweat samples, being 31 obtained from patients with cystic fibrosis (CF). Sweat was collected by quantitative pilocarpine iontophoresis in the Macroduct system for 30 minutes. Samples were immediately determined by Sweat-Chek analyzer (Wescor) and sodium quantification with a flame photometer. RESULTS: In non-CF subjects sweat (n=175), mean conductivity and quantitative sodium were 41mmol/L (16-75mmol/l) and 36mEq/ l (12-75mEq/l) respectively. In CF subjects (n=31), mean values of conductivity and sodium were 119mmol/L (84-155mmol/l) and 113mEq/l (80 - 146mEq/l) respectively. None of CF patients showed values lower than 80mmol/L. There was a correlation between sweat conductivity and sodium determination (r= + 0.99; p<0.0001). CONCLUSION: Sweat conductivity by Wescor simplifies the analysis with lower volumes and is well correlated to sodium concentration.