Background. The sweat test (ST) remains the main test for Cystic fibrosis (CF) diagnosis and it is now also used to evaluate the function of the CFTR protein in basal conditions and under the influence of CFTR modulators. However it is not yet well-defined the biological variability of the test, both among different individuals (inter-individual) and within the same individual at different times and under different conditions (intra-individual).

Hypothesis and objectives. The project aims to study intra-individual sweat chloride (Cl) biological variability both in subjects with CF and in healthy people and to assess its possible correlation to different variables  (diet, seasons, menstrual cycle).