CFTR and cystic fibrosis: The diagnosis of CF by each physician was established based on international criteria (Farrell et al., 2008), i.e., the presence of characteristic clinical features, such as lung disease and/or gastrointestinal symptoms, and evidence of CFTR dysfunction, either by a two positive SwCl tests (≥60 mEq/L) and/or the identification of two CF-causing mutations.