Rapid method for the detection of cystic fibrosis of the pancreas in children.

One of the main criteria for the diagnosis of cystic fibrosis of the pancreas is the presence of a raised sweat sodium level in the patient (Di Sant' Agnese, Darling, Perera, and Shea, 1953). The standard method of using pilocarpine iontophoresis to produce sweat (Gibson and Cooke, 1959), and estimating the sodium present by conductivity or flame photometry, is a workable technique but has some drawbacks. Considerable discomfort is experienced by some patients and the process is timeconsuming, as it takes at least 30 minutes to obtain sufficient sweat for a reliable sodium determination. Pilocarpine iontophoresis is therefore not suitable for routine use as a screening test on large numbers of patients. The use of a sodium responsive electrode for direct readings of the sodium concentration of sweat has not been successful in our hands (Goldbloom and Sekelj, 1964). We found that iontophoresis was necessary before reliable readings could be obtained. Difficulties also occurred due to sweat evaporation and variations in skin temperature. McGrady and Bessman (1955) and Johnston (1956) have found that cystic fibrosis patients have a raised parotid saliva sodium level compared with that of normal subjects. We have devised a method for measuring the sodium concentration of unstimulated parotid saliva using a micro-dual sodium electrode, which is simple and reliable in children and adults. The results are presented of a trial with this electrode on normal subjects, cystic fibrosis heterozygotes, and cystic fibrosis homozygotes.