Some practical simplifications of perspiration electrolyte analysis ("sweat test").

C sric FIBROSIS of the pancreas is now acknowledged to be one of the most serious chronic diseases of childhood, with an estimated incidence in its fully manifested form of 1-1.7 per 1000 live births (1). Chances for early diagnosis and treatment-essential before the pulmonary disease that dominates the clinical picture has caused irreversible changes-were greatly enhanced with the introduction of perspiration electrolyte analysis (the “sweat test”) by Shwachinan (2) and others, following the reports by Darling et at. and di Sant ‘Agnese et at. (3, 4) of uniquely elevated sodium and chloride concentrations in the sweat of 99 per cent of patients with cystic fibrosis of the pancreas. The quantitative “sweat test” because of its inherent reliability, relative simplicity, and generally clear-cut results has become the cornerstone for diagnosis of cystic fibrosis (1), and remains preferable to the several recently proposed simplifications, screening tests, or substitute procedures (5-10). The originally proposed and widely adopted “sweat test” technic (2) consisted essentially of absorption of 1 gm. or more of perspiration by a pre-weighed gauze pad from midback or midabdomen of the plastic-bag-enclosed patient who was under thermal stress stimulation. This was followed by elution of