Portable Sequencer Gains Traction in Rare Disease Diagnosis Amid Clinical Validation Efforts

A validation study conducted by the University Medical Center Utrecht in the Netherlands demonstrated that Oxford Nanopore’s sequencing technology shows promise for diagnosing rare diseases but is not yet ready for clinical application. The center, one of eight rare disease diagnostic centers in the Netherlands, performs approximately 19,000 molecular and cytogenetic tests annually.

The research team performed Nanopore sequencing on 123 patient samples with known variants. They found that Nanopore sequencing was comparable to Illumina sequencing in detecting single-nucleotide polymorphisms (SNPs) and small insertions and deletions (indels). However, 13 out of 66 copy number variations (CNVs) were missed (a false-negative rate of 20%), half of which were smaller than 100 kb. The team stated that most of the missed CNVs could be recovered by optimizing bioinformatics analysis tools, but this level of performance is not yet achievable with "out-of-the-box" solutions.

Nanopore long-read sequencing offers numerous technical advantages, enabling the detection of structural variants, short tandem repeats, and methylation. In theory, it can replace multiple testing methods such as PCR, gene chips, and FISH to achieve "all-in-one" comprehensive analysis. However, this study clearly highlights the gap between research-grade technology and clinical-grade tools.

The issues are concentrated in several areas: significant yield variability across different flow cells (ranging from 30 GB to over 100 GB), insufficient reliability of CNV detection tools in low-coverage and repetitive sequence regions, and the need for substantial development of data visualization and quality control tools. The principal investigator stated plainly that a bioinformatics team is required for customized development, which will take time. This presents a realistic barrier for most hospital laboratories.

UMC Utrecht pioneered the introduction of next-generation sequencing in 2011 and was the first to implement whole-exome sequencing in 2014. Earlier this year, it transitioned to short-read whole-genome sequencing to cover all clinical indications. The institution aims to switch to long-read whole-genome sequencing next year. However, research findings indicate that current technologies are not yet mature enough.

Meanwhile, the center is also evaluating Illumina’s TruPath Genome technology. Approaches leveraging short-read sequencing with extended genomic coverage are advancing. The clinical sequencing market is evolving into a landscape where multiple technological pathways coexist: Illumina’s short-read platforms offer higher accuracy but limited variant type coverage; Nanopore’s long-read technologies provide more comprehensive information but pose higher barriers in bioinformatics analysis; and PacBio is competing with intermediate solutions. For hospitals, the choice of technology involves not only performance but also considerations such as bioinformatics team staffing, data storage costs, and IT infrastructure investments. The conclusion drawn by UMC Utrecht applies to the entire industry: several more rounds of iteration are needed before single-molecule sequencing becomes fully established in clinical practice.

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