Collecting sweat in patients with cystic fibrosis [letter].

Dr. Soldin describes a method of collecting sweat for the diagnosis of 
cystic fibrosis which involves placing the patient on an electric blanket 
and wrapping him warmly for 2 - 5 hours until profuse 
sweating has occurred for 30 minutes. One important omission from the 
title and the abstract is any mention of safety. Children with 
cystic fibrosis may develop heat prostration when exposed to high temperatures, 
which may cause massive sodium and chloride losses via the sweat. 
This could occur with the method described. The apparatus described by 
Gibson and Cooke in the classic pilocarpine iontophoresis method of collecting 
sweat is neither overly sophisticated nor expensive. It remains the method 
of choice, although attention to detail is important. 