Targeted capture sequencing in a large LQTS family reveals a new pathogenic mutation c.2038delG in KCNH2 initially missed due to allelic dropout

Repeat genetic testing with targeted capture sequencing in primary arrhythmia syndrome and cardiomyopathy

In inherited primary arrhythmia syndromes (PAS) and cardiomyopathies (CMP), the yield of genetic testing varies between 20 and 75% in different diseases according to studies performed in the pre next-generation sequencing (NGS) era. It is unknown whether retesting historical negative samples with NGS techniques is worthwhile. Therefore, we assessed the value of NGS-based panel testing in previously genotype negative-phenotype positive probands. We selected 107 patients (47 PAS and 60 CMP) with a clear phenotype who remained genotype negative after genetic analysis of the main genes implicated in their specific phenotype. Targeted sequencing of the coding regions of 71 PAS- and CMP-related genes was performed. Variant interpretation and classification was done according to a cardiology-specific scoring algorithm ('Amsterdam criteria') and the ACMG-AMP criteria. Co-segregation analysis was performed when DNA and clinical data of family members were available. Finally, a genetic diagnosis could be established in 21 patients (20%), 5 PAS (11%) and 16 CMP (27%) patients, respectively. The increased detection rate was due to sequencing of novel genes in 52% of the cases and due to technical failures with the historical analysis in 48%. A total of 118 individuals were informed about their carrier state and either reassured or scheduled for proper follow-up. To conclude, genetic retesting in clinically overt PAS and CMP cases, who were genotype negative with older techniques, resulted in an additional genetic diagnosis in up to 20% of the cases. This clearly supports a policy for genetic retesting with NGS-based panels.