Frequency of the cystic fibrosis 3199del6 mutation in individuals heterozygous for I148T

Purpose: To determine the carrier frequency of the 3199del6 cystic fibrosis (CF) mutation in individuals heterozygous for I148T in a large-scale CF testing population. Methods: DNA samples from 439 consecutive I148T-heterozygous individuals were screened for the 3199del6 mutation using a laboratory-developed test. Results: Genotyping revealed four samples heterozygous for the 3199del6 mutation (0.9%). The four samples positive for 3199del6 had an IVS 8 genotype of 7T/9T. The 3199del6 mutation was not observed after genotyping of 348 random, anonymous samples. Conclusion: The 3199del6 mutation occurs in 0.9% of individuals positive for the 1148T mutation and < 0.07% of chromosomes that are wild type for the ACMG panel mutations.