ELECTRICAL CONDUCTIVITY OF SWEAT

Abstract

A practical and simple method for measuring conductivity of sweat has been described. A close correlation was found between the results from 367 patients tested by the routine Pilocarpine iontophoresis method with chemical determinations of the chloride, sodium, and potassium in sweat eluted from pads and by the described conductivity method. The high conductivity values noted in 40 patients with cystic fibrosis serve to distinguish these patients from all others. Only one patient given a diagnosis of cystic fibrosis gave a conductitvity scale reading of less than 100. Although this is a semi-quantitative method, it could serve a useful purpose in the small laboratory where technicians experienced in the performance of the quantitative sweat tests are not available. Standardization of equipment is essential, as is constant checking by using standard test solutions. When borderline values are encountered by the conductivity method with values between 80 and 100 scale units, quantitative electrolyte determinations may also yield borderline concentrations and are the determinations we recommend. Age is a factor in interpretation of the conductivity of sweat, as the values increase with age in parallel with the sweat electrolyte concentration. In small infants, especially those malnourished or dehydrated, one may encounter some difficulty in obtaining an adequate sweat specimen.