Sweat tests to diagnose cystic fibrosis in adults

Br Med J (Clin Res Ed). 1983 Apr 30;286(6375):1381-3. doi: 10.1136/bmj.286.6375.1381.


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.

MeSH terms

  • Adolescent
  • Adult
  • Cystic Fibrosis / diagnosis*
  • Cystic Fibrosis / metabolism
  • Female
  • Fludrocortisone
  • Humans
  • Male
  • Reference Values
  • Sodium / analysis*
  • Sweat / analysis*


  • Sodium
  • Fludrocortisone