Sweat sulfate concentrations are decreased in cystic fibrosis

We have developed methods to measure inorganic sulfate in small volumes of sweat, and compared sulfate concentrations in sweat samples from CF patients and controls. In contrast to the increases in sweat chloride, sweat sulfate concentrations in 13 CF patients were reduced to 68 +/- 24% of control values (mean +/- SD, n = 25, p less than 0.001). Sulfate concentrations in sweat may depend on sweat rates, but the rates were not significantly different in the two study groups. Since we have observed a positive correlation between sweat sulfate and sweat chloride excretion in non-CF subjects in earlier studies, we suggest that the decreased sulfate in CF sweat may bear directly on the nature of the anion permeability defect present in the ductal epithelium of the CF sweat gland.