BACKGROUND: Cystic fibrosis (CF) is an autosomal recessive condition that has an 
incidence of 1:2500 live births in Northern Europe. Due to the large number of 
mutations that can result in classical or atypical CF phenotype, the sweat test, 
which quantifies the amount of chloride and sodium in sweat, is vital in 
supporting the diagnosis of CF. Patients with CF have raised concentrations of 
chloride and sodium in their sweat; however, it is the concentration of chloride 
in sweat which provides the greatest diagnostic sensitivity for CF.
METHOD: An inductively coupled plasma mass spectrometry (ICP-MS) method for the 
analysis of sweat chloride and sodium was evaluated for the routine measurement 
of sweat collected using the Wescor Macroduct(®) Sweat Collection System. The 
precision, linearity and agreement with the all laboratories trimmed means 
(ALTMs) and 'weighed-in' concentrations of sodium and chloride in samples 
supplied by the UK NEQAS external quality assessment (EQA) Sweat Testing Scheme 
were assessed.
RESULTS: This ICP-MS method for the quantification of chloride and sodium in 
sweat samples was shown to be accurate, precise and suitable for the routine 
analysis of sweat chloride and sodium.
CONCLUSION: The method performs well and is now used in the routine analysis of 
sweat in this laboratory.