CFTR and cystic fibrosis: Overall, based on CFTR-mediated Cl− secretion in the colon and subsequent confirmatory CF diagnostic testing (sweat Cl−, CFTR genotypes and clinical outcomes (data on Table S1-b), we could classify the individuals in the “CF suspicion:” group (n = 49) as: Classic CF (n = 9), Non-Classic CF (n = 7), CFTR-RD (n = 2) and Non-CF (n = 26).