Diagnosing cystic fibrosis in adults [letter].

Gordeuk et al. state that cystic fibrosis may be first diagnosed in 
adulthood, but we feel that a condition with such grave genetic 
and prognostic implications must be diagnosed with special caution in this 
age group. In particular, the sweat test, which is the main 
diagnostic tool for use with children, must be interpreted in adults 
in the light of possible age-related increases in normal sweat-electrolyte concentration 
and other factors that may affect the assay. Although it is 
generally accepted that "normal" sweat sodium and chloride concentrations are higher 
in adults than in children, there is no clear agreement about 
the upper limits of the normal range in adults. The volume 
of sweat produced during the test may also have a substantial 
effect on electrolyte values. For the diagnosis of cystic fibrosis in 
adults, an attempt should thus be made to base the diagnosis 
not only on "elevated" sweat-electrolyte values and clinical impression but also 
on pancreatic-function data. 