Neuromuscular diseases (NMDs) are a group of over 200 highly genetically as well as clinically heterogeneous inherited genetic disorders that affect the peripheral nervous and muscular systems, resulting in gross motor disability. The clinical and genetic heterogeneities of NMDs make disease diagnosis complicated and expensive, often involving multiple tests. To expedite the molecular diagnosis of NMDs, the authors designed and validated several next-generation sequencing (NGS)-based comprehensive gene panel tests that include complementary deletion and duplication testing through comparative genomic hybridization arrays (aCGH). This validation established the targeted gene panel test to have 100% sensitivity and specificity for single nucleotide variant detection. To compare the clinical diagnostic yields of single gene (NMD associated) tests with the various NMD NGS panel tests, the authors analyzed data from all clinical tests performed at the Emory Genetics Laboratory (EGL) from October 2009 through May 2014. They further compared the clinical utility of the targeted NGS panel test with that of exome sequencing (ES). The results reveal that NMD comprehensive panel testing has a 3-fold greater diagnostic yield (46%) than single gene testing (15-19%). Sanger fill-in of low-coverage exons, copy number variation (CNV) analysis, and thorough in-house validation of the assay all complement panel testing and allow the detection of all types of causative pathogenic variants, some of which (about 18%) may be missed by ES. These results strongly indicate that for molecular diagnosis of heterogeneous disorders like NMD, targeted panel testing has the highest clinical yield and should therefore be the preferred first-tier approach.
