Long-Read Genome Sequencing Proposed as a First-Line Test for Rare Genetic Diseases

Researchers from Radboud University Medical Center and Maastricht UMC+ have proposed that long-read genome sequencing could become a first-line tool for diagnosing rare genetic diseases. The clinical study, published in the New England Journal of Medicine, compared current diagnostic workflows with long-read sequencing in 1,000 patients.

The research team said this method can present DNA structure more completely than the short-read sequencing currently in common use and increased the number of diagnoses by about 3%. They also noted that long-read sequencing has the potential to replace as many as 15 separate tests, making the diagnostic process more centralized and faster.

Rare diseases each affect small numbers of patients, but their overall burden is not small. The press release noted that as many as 400 million people worldwide may be affected by rare diseases, and that most rare diseases have genetic causes. For patients and families, a confirmed diagnosis is not only a name for the disease; it may also affect understanding of prognosis, assessment of family risk, and arrangements for follow-up care.

The key difference with long-read sequencing is that it reads longer DNA fragments at one time. Current methods often use fragments of about 300 bases and then assemble them; long-read technology can read fragments as long as about 20,000 bases, making it easier to identify large structural variants, repeat sequences, or other regions that are more difficult for short-read technology to resolve.

The researchers also emphasized that long-read sequencing can simultaneously capture signals from external DNA modifications. Such modifications may affect gene switches and, in some cases, are also related to disease; under current workflows, they often require additional specialized testing. If the same platform can obtain both sequence and modification information at the same time, clinical laboratory workflows may change as a result.

However, this claim still needs to be interpreted in the context of implementation conditions. The press release did not provide details on disease categories, cost-effectiveness, consistency of interpretation across different laboratories, or insurance reimbursement; for long-read sequencing to become a widely used first-line test, it still needs to prove that it is equally feasible in diverse populations and different healthcare systems.

The current significance is that genetic diagnosis for rare diseases is moving from “checking items one by one” toward more integrated whole-genome analysis. If subsequent research and clinical deployment can confirm its benefits, long-read sequencing may shorten the long diagnostic journey for some patients; but whether it can comprehensively replace existing tests will still depend on accumulated evidence, professional interpretation capacity, and allocation of healthcare resources.