A methodological study of the diagnosis of cystic fibrosis by instrumental neutron activation analysis of sodium in nail clippings.

Instrumental neutron activation analysis (INAA) of nail clippings was used in the 
development of a diagnostic method for cystic fibrosis (CF). From CF 
patients and controls more than three years old, nail clippings were 
sampled for tests of different errors. As a result of this 
study a precise collection routine was outlined. Sodium is easily washed 
out from nail clippings. The risk of sodium contamination of the 
nails seems to be small. The sodium distribution in the nail 
is inhomogeneous, and the sodium content varies also from nail to 
nail in the same person. There is good evidence that the 
increased sodium in the nails of CF patients comes from the 
sweat. There seems to be a basic "intrinsic" sodium level, which 
is about the same in the nails of CF patients as 
in controls. The precision and accuracy of INAA for determining sodium 
in nails is considered satisfactory. It is concluded that INAA of 
the sodium concentration in nail clippings is a suitable method as 
an aid in the diagnosis of CF if a precise collection 
routine is used. 