THE SWEAT TEST

Abstract

AN INCREASED interest in the physiology of sweating was precipitated by the demonstration of markedly elevated electrolyte levels in sweat of patients with cystic fibrosis. Indeed, the determination of sweat electrolytes has become the most reliable single diagnostic test for cystic fibrosis, replacing the more difficult, time consuming, uncomfortable, and less reliable procedures of duodenal fluid aspiration and assay. The marked reduction or absence of proteolytic activity of duodenal fluid no longer serves as the cornerstone of diagnosis, since fully 15% of patients with cystic fibrosis have sufficient exocrine pancreatic function to yield normal or nearly normal enzyme values. Nevertheless, study of duodenal fluid is still of considerable value when dealing with cases difficult to diagnose, in instances of borderline sweat electrolyte levels, or for special study purposes.