Australasian guideline for the performance of sweat chloride testing 3rd edition: to support cystic fibrosis screening, diagnosis and monitoring

The sweat test is used as a biological marker of cystic fibrosis transmembrane conductance regulator (CFTR) dysfunction, but there is growing recognition that sweat chloride concentrations of people with cystic fibrosis (CF) can overlap with those without CF. There are also people without CF whose symptoms are caused by abnormalities of CFTR. To support clinical decisions, the sweat chloride test conducted appropriately should provide consistent results between laboratories and common decision limits should be used. International consensus guidelines now recommend a standard set of clinical decision limits for sweat chloride, with values between 30 and 59 mmol/L, as the intermediate result for all ages. It is therefore timely to update the Australasian guideline decision limits to align with international consensus guidelines and peak body recommendations. At the same time, the technical aspects for performance of the sweat chloride test should be reviewed. This paper updates (and replaces) the guideline for the performance of the sweat chloride test that were last published by the AACB in 2017. This freely available guideline was developed to support Australasian laboratories, and laboratories from other regions, with the accurate performance of sweat chloride testing. The guideline provides 16 recommendations for the performance of the sweat chloride test encompassing the total testing process. Previous recommendations related to sweat conductivity testing have been removed from this guideline. The sweat chloride decision limits of ≥30 mmol/L support a review by a CF physician for all age groups. Sweat chloride concentrations of ≥60 mmol/L are supportive of a diagnosis of CF.