Leveraging the power of new molecular technologies in the clinical setting requires unprecedented awareness of limitations and drawbacks: experience of one diagnostic laboratory.

BACKGROUND: Advances in molecular technologies and in-silico variant prediction tools offer wide-ranging opportunities in diagnostic settings, yet they also present with significant limitations. OBJECTIVE: Here, we contextualise the limitations of next-generation sequencing (NGS), multiplex ligation-dependent probe amplification (MLPA) and in-silico prediction tools routinely used by diagnostic laboratories by reviewing specific experiences from our diagnostic laboratory. METHODS: We investigated discordant annotations and/or incorrect variant 'callings' in exons of 56 genes constituting our cardiomyopathy and connective tissue disorder NGS panels. Discordant variants and segmental duplications (SD) were queried using the National Center for Biotechnology Information (NCBI) Basic Local Alignment Search Tool and the University of California Santa Cruz genome browser, respectively, to identify regions of high homology. Discrepant variant analyses by in-silico models were re-evaluated using updated file entries. RESULTS: We observed a 5% error rate in MYH7 variant 'calling' using MLPA, which resulted from >90% homology of the MYH7 probe-binding site to MYH6. SDs were detected in TTN, PKP2 and MYLK. SDs in MYLK presented the highest risk (15.7%) of incorrect variant 'calling'. The inaccurate 'callings' and discrepant in-silico predictions were resolved following detailed investigation into the source of error. CONCLUSION: Recognising the limitations described here may help avoid incorrect diagnoses and leverage the power of new molecular technologies in diagnostic settings.

Genetic Diagnostic Testing for Inherited Cardiomyopathies: Considerations for Offering Multi-Gene Tests in a Health Care Setting.

Inherited cardiomyopathies (ICs) are a major cause of heart disease. Given their marked clinical and genetic heterogeneity, the content and clinical utility of IC multi-gene panels has been the topic of continuous debate. Our genetics diagnostic laboratory has been providing clinical diagnostic testing for ICs since 2012. We began by testing nine genes and expanded our panel by fivefold in 2015. Here, we describe the implementation of a cost-effective next-generation sequencing (NGS)-based assay for testing of IC genes, including a protocol that minimizes the amount of Sanger sequencing required to confirm variants identified by NGS, which reduces the cost and time of testing. The NGS assay was developed for the simultaneous analysis of 45 IC genes and was assessed for the impact of panel expansion on variant detection, turnaround time, and cost of testing in a cohort of 993 patients. The assay led to a considerable reduction in test cost and turnaround time. However, only a marginal increase was observed in the diagnostic yield, whereas the rate of inconclusive findings increased considerably. These findings suggest that the ongoing evaluation of gene content and monitoring of clinical utility for multi-gene tests are essential to achieve maximum clinical utility of multi-gene tests in a publicly funded health care setting.