Reference intervals for sweat chloride

According to the CFF disease registry, 1.7% of CF patients had sweat chloride concentrations less than 60mmol/L (mean of 45.1mmol/L) and 0.5% had sweat chloride concentrations 40 mmol/L. These patients were diagnosed with CF on the basis of genotyping, nasal transepithelial potential difference studies, and clinical presentation.  

There is a lack of consensus on the appropriate decision limit for sweat conductivity. The CFF states that a patient with a sweat conductivity 50 mmol/L should be referred for a confirmatory sweat chloride test, and Wescor recommends that conductivity values up to 60 mmol/L can be considered normal, and concentrations 80 mmol/L are positive for 

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