To the Editor: Cystic fibrosis (OMIM 219700) is one of the most common autosomal recessive disorders in Caucasians. It is caused by mutations in the CFTR 1 [cystic fibrosis transmembrane conductase regulator (ATP-binding cassette sub-family C, member 7)] gene, located on chromosome 7q31.2. The frequency of the most common mutation, p.Phe508del (F508del, c.1521_1523delCTT), varies markedly among ethnic groups, but is always tested in both patient testing and carrier screening (1, 2). At our institution, we screen for CFTR mutations with high-resolution melting analysis (LightScanner®; Idaho Technology). The method consists of PCR amplification of the fragment in question in the presence of a fluorescent dye (LCGreen Plus) that intercalates between bases in double-stranded DNA. The amplification products are melted after the PCR to reveal unique melting profiles according to their sequence compositions (3). A successful experiment depends on primer design (gene scanning) and probe design (genotyping), as well as on …