[Sweat test evolution in cystic fibrosis patients treated with Elexacaftor/Tezacaftor/Ivacaftor]

The chloride (Cl-) sweat test remains the reference test in the diagnosis of cystic fibrosis, allowing direct assessment of CFTR (Cystic Fibrosis Transmembrane conductance Regulator) channel function. Under highly effective modulators such as the combination of Elexacaftor, Tezacaftor and Ivacaftor (ETI), the Cl- level in sweat significantly improves, as shown in our cohort of patients when ETI was introduced. In addition to its role in the diagnosis of the disease, the sweat test is also important for individual clinical trials (n-of-1) in patients not eligible for ETI and for newborn screening for cystic fibrosis.