Sweat tests to diagnose cystic fibrosis in adults.
Br Med J (Clin Res Ed) 1983; 286 doi: https://doi.org/10.1136/bmj.286.6375.1381 (Published 30 April 1983) Cite this as: Br Med J (Clin Res Ed) 1983;286:1381- M E Hodson,
- I Beldon,
- R Power,
- F R Duncan,
- M Bamber,
- J C Batten
Abstract
Twenty five patients with cystic fibrosis and 25 controls were studied to define a sweat sodium concentration in adults that could be taken as diagnostic of cystic fibrosis. Some of the controls had a sweat sodium concentration of over 50 mmol(mEq)/l, and thus cystic fibrosis should be diagnosed in an adult only when two measurements of sweat sodium concentration are above 70 mmol/l. In cases in which the sweat sodium concentration was borderline a suppression test using fludrocortisone improved the accuracy of diagnosis; this test entails recording the lowest concentration reached after administration of the drug. A scatter diagram of the baseline sweat sodium concentrations plotted against the lowest concentration attained after suppression with fludrocortisone may aid the diagnosis further.