Isolated Nonvisualization of the Fetal Gallbladder Should Be Considered for the Prenatal Diagnosis of Cystic Fibrosis.

BACKGROUND: Cystic fibrosis (CF) can be revealed during fetal life by diverse ultrasound digestive abnormalities (USDA) such as fetal echogenic bowel or fetal intestinal loop dilatation, nonvisualization of the fetal gallbladder (NVFGB) being rarely observed in isolation. Only 6 cases of CF revealed by isolated NVFGB have been reported so far in the literature. Furthermore, recent studies suggested that this sign is of poor predictive value for CF. METHODS: We report on the results of a 6-year French tricenter study on 1,124 cases of fetal USDA for whom a comprehensive molecular study was performed for CF. RESULTS: Among the 37 CF fetuses, 5 (13.5%) presented with isolated NVFGB at ultrasound (US) examination at 24-31 weeks of gestation. This sign was more frequently observed in CF fetuses than in non-CF fetuses, with a likelihood ratio of 2.7. The genotypes included three c.1521_1523del (F508del) homozygous cases and two compound heterozygous cases for a frequent and a rare CF-causing variant. DISCUSSION: These observations highlight the importance to report on the presence and aspect of the fetal gallbladder at the second trimester US scan and to consider prenatal CFTR molecular analysis in cases of isolated NVFGB.

Multicenter validation study for the certification of a CFTR gene scanning method using next generation sequencing technology.

BACKGROUND: Many European laboratories offer molecular genetic analysis of the CFTR gene using a wide range of methods to identify mutations causative of cystic fibrosis (CF) and CFTR-related disorders (CFTR-RDs). Next-generation sequencing (NGS) strategies are widely used in diagnostic practice, and CE marking is now required for most in vitro diagnostic (IVD) tests in Europe. The aim of this multicenter study, which involved three European laboratories specialized in CF molecular analysis, was to evaluate the performance of Multiplicom's CFTR MASTR Dx kit to obtain CE-IVD certification. METHODS: A total of 164 samples, previously analyzed with well-established "reference" methods for the molecular diagnosis of the CFTR gene, were selected and re-sequenced using the Illumina MiSeq benchtop NGS platform. Sequencing data were analyzed using two different bioinformatic pipelines. Annotated variants were then compared to the previously obtained reference data. RESULTS AND CONCLUSIONS: The analytical sensitivity, specificity and accuracy rates of the Multiplicom CFTR MASTR assay exceeded 99%. Because different types of CFTR mutations can be detected in a single workflow, the CFTR MASTR assay simplifies the overall process and is consequently well suited for routine diagnostics.

A false positive newborn screening result due to a complex allele carrying two frequent CF-causing variants.

The detection of two frequent CFTR disease-causing variations in the context of a newborn screening program (NBS) usually leads to the diagnosis of cystic fibrosis (CF) and a relevant genetic counseling in the family. In the present study, CF-causing variants p.Phe508del (F508del) and c.3140-26A>G (3272-26A>G) were identified on a neonate with positive ImmunoReactive Trypsinogen test by the Elucigene™ CF30 kit. The CF diagnosis initially suggested, despite three inconclusive Sweat Chloride Tests (SCT), was finally ruled out after the familial segregation study combined with a negative SCT. Haplotype studies, based on the comparison of 80 p.Phe508del haplotypes, suggested a probable de novo occurrence of c.3140-26A>G on the p.Phe508del ancestral allele in this family. This false positive case emphasizes the importance of SCT in the NBS strategy. Moreover, it raises the need for familial segregation studies in CF and in overall molecular diagnosis strategy of autosomal recessive diseases.