Background
As DNA sequencing costs decline, genetic testing options have expanded. Whole exome and whole genome sequencing (WGS) are entering clinical use, posing questions about their incremental value compared with disease-specific multi-gene panels that have been the cornerstone of genetic testing.
Methods and Results
Forty-one patients with hypertrophic cardiomyopathy (HCM) who had undergone targeted HCM genetic testing (either multi-gene panel or familial variant test) were recruited into the MedSeq Project, a clinical trial of WGS. Results from panel genetic testing and WGS were compared. In 20 of 41 participants panel genetic testing identified variants classified as pathogenic, likely pathogenic or uncertain significance (VUS). WGS identified 19 of these 20 variants but the variant detection algorithm missed a pathogenic 18-base pair duplication in MYBPC3 due to low coverage. In 3 individuals, WGS identified variants in genes implicated in cardiomyopathy but not included in panel testing: a pathogenic PTPN11 variant and VUSs in ILK and FLNC. WGS also identified 84 secondary findings (mean=2/person, range= 0–6), which mostly defined carrier status for recessive conditions.
Conclusions
WGS detected nearly all variants identified on panel testing, provided one new diagnostic finding, and allowed interrogation of posited disease genes. Several variants of uncertain clinical utility and numerous secondary genetic findings were also identified. While panel testing and WGS provided similar diagnostic yield, WGS offered the advantage of re-analysis over time to incorporate advances in knowledge, but necessitated expertise in genomic interpretation to appropriately incorporate WGS into clinical care.