The sweat test in the diagnosis of fibrocystic disease of the pancreas.

The sweat test for the diagnosis of fibrocystic disease of the pancreas owes its origin to an observation made during the heat wave of 1948 in New York (Kessler and Andersen, 1951) that more than half of the children admitted to hospital with signs of heat prostration were cases of fibrocystic disease of the pancreas. Although the serum sodium and chloride concentrations were much reduced the children had no history of prolonged vomiting, intestinal loss, kidney or adrenal dysfunction. It was postulated that there was some derangement of the sweating mechanism and that excessive electrolyte loss may have occurred through the skin. In 1953 a preliminary report was published of the sodium and chloride concentrations in the sweat from eight patients with fibrocystic disease of the pancreas together with those from a similar number of control patients of the same age group (Darling, di Sant'Agnese, Perera, and Andersen). This showed that the former group excreted four to five times as much sodium and chloride in the sweat as did the controls. Di Sant'Agnese, Darling, Perera, and Shea (1953) later published a much larger series of results which have confirmed the earlier findings of the persistently high concentration of sodium and chloride in the sweat of patients with fibrocystic disease of the pancreas. The purpose of this communication is to report a similar series of investigations done in Sheffield Children's Hospital. An attempt is also made to compare the value of the sweat test with that of other laboratory tests usually performed on patients with steatorrhoea, failure to thrive, and chronic respiratory lesions.