Evaluation of an inductively coupled plasma mass spectrometry method for the analysis of sweat chloride and sodium for use in the diagnosis of cystic fibrosis

Abstract

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. 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. 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. The method performs well and is now used in the routine analysis of sweat in this laboratory.