3.2 CFTR mutation carrying status
CFTR mutation was not detected in 7 subjects, and 14 CFTRmutations were detected in the remaining 18 subjects. The relationship between the detected mutations and disease was evaluated according to the general criteria of United States College of Medical Genetics and Genomics (ACMG). We found that one sites was Likely Pathogenic, five were a Variant of Uncertain Significance (VUS), and the rest were graded as Benign. These sites were searched in ClinVar database, and no CF pathogenic sites were found. The China population database provided by Beijing Mygenostics co., Ltd. (included 46648 Han people in the Chinese mainland area) was selected to query the carrying rate of these mutations. The MAF of 6 sites was>0.05, which was the SNPs in the population (Table S1). The whole blood of the parents of the 7 patients with non-SNPs was collected for first-generation verification, and it was found that these mutations came from one parent (Table S2). The patients with no CFTR mutation or only one mutation were tested for Multiplex Ligation-dependent Probe Amplification (MLPA), and the results were negative. In combination with past medical history, family history, sweat chloride level test (SCLs, all lower than 60 mmol/L) and preoperative chest X-ray, it can be determined that all the enrolled children in this study were excluded from the diagnosis of CF.