Diagnosing mitochondrial disorders is a challenge due to the heterogeneous clinical presentation and large number of associated genes. A custom next generation sequencing (NGS) panel was developed incorporating the full mitochondrial genome (mtDNA) plus 19 nuclear genes involved in structural mitochondrial defects and mtDNA maintenance. This assay is capable of simultaneously detecting small gene sequence variations and larger copy number variants (CNVs) in both the nuclear and mitochondrial components along with heteroplasmy detection down to 5%. We describe technical validations of this panel and its implementation for clinical testing in a Canadian reference laboratory, and report its clinical performance in the initial 950 patients tested. Using this assay, we demonstrate a diagnostic yield of 18.1% of patients with known pathogenic variants. In addition to the common 5 kb mtDNA deletion, we describe significant contribution of pathogenic CNVs in both the mitochondrial genome and nuclear genes in this patient population.

中文翻译：

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核线粒体下一代测序和拷贝数变异分析组合板在加拿大人群中的验证和临床表现

由于临床表现的异质性和大量相关基因的存在，诊断线粒体疾病是一个挑战。开发了定制的下一代测序（NGS）面板，其中包含完整的线粒体基因组（mtDNA）以及涉及结构线粒体缺陷和mtDNA维护的19个核基因。该测定法能够同时检测核和线粒体成分中的小基因序列变异和较大的拷贝数变异（CNV），以及低至5％的异质性检测。我们描述了该专家组的技术验证及其在加拿大参考实验室中进行临床测试的实施情况，并报告了其在最初测试的950名患者中的临床表现。使用该测定，我们证明了18.1％的已知病原体变异患者的诊断率。