Development of a screening system for cystic fibrosis.

We have developed a simple method for detecting high concentrations of chloride in sweat from ambulatory subjects, a measurement useful in the detection of cystic fibrosis. The method is based on the standard approach of stimulating sweat generation through iontophoresis of pilocarpine nitrate into the skin, followed by collection and analysis of the sweat for chloride concentration. The sweat-stimulating reagents are contained in polymeric gel pads, which are used in conjunction with a small battery-powered stimulator. The chloride analysis is subsequently done on the stimulated site by use of a thin test patch that picks up a fixed amount of sweat and changes color if the chloride concentration is higher than a predetermined value. The successful completion of a test is indicated by a fill tab, which changes color when the appropriate amount of sweat has been picked up by the chloride test patch.