Cystic-fibrosis heterozygosity in childhood bronchial asthma [letter].

We found that the Szczepanski bromide test, which we simplified with the 
aid of ion-sensitive electrode, is suitable for the detection of C.F. 
heterozygosity in most cases. We examined the sweat of 74 randomly 
selected children with respiratory asthma during the past 2 years, the 
sodium and chloride concentrations and bromide index being determined. Sodium and 
chloride concentrations in the sweat of the asthma children were slightly 
but significantly higher (P < 0.05) than those of the controls. 
The difference in bromide index was even more significant (P < 
0.01). This suggests that C.F. gene carriers are unusually prevalent among 
children with bronchial asthma. One possibility is that enhanced ion loss 
in various diseases with allergic pathological mechanisms is secondary in nature. 
However, this seems unlikely since in our material high sweat-electrolyte concentrations 
were observed in only a proportion of control children whose illness 
was similar in severity to that of the asthmatic children, and 
normal sweat values were obtained even when the child's condition was 
very serious. 