Comparison of quantitative sweat chloride methods after positive newborn screen for cystic fibrosis

Objectives Rapid and reliable confirmatory sweat testing following a positive newborn screen (NBS) for cystic fibrosis (CF) is preferred to allow for early diagnosis and to decrease parental anxiety. The Cystic Fibrosis Foundation (CFF) recently recommended a quantity not sufficient (QNS) rate of ≤ 10% in infants < 3 months of age referred for quantitative sweat chloride analysis. Two CFF-approved methods are available by which to quantitatively measure chloride concentration in sweat. Our objective was to compare the performance of the Macroduct® sweat collection system (MSCS) with the Gibson and Cooke technique (GCT) in the acquisition of samples for the determination of sweat chloride concentration in infants with a positive Minnesota State NBS for cystic fibrosis.