This post was written by Charlotte Harrison, Freelance Science Writer
Whole genome sequencing detects neurological disorders
Genetic testing using whole genome sequencing could put an end to years of uncertainty for people with under-diagnosed neurological conditions, according to a new study published in the Lancet Neurology.
Several neurological disorders, including Fragile X syndrome (an intellectual disability), Huntington’s disease, Friedreich’s ataxia (a movement disorder) and some forms of dementia are classed as repeat expansion disorders. This group of disorders, caused by expansions of short repetitive DNA sequences, have overlapping symptoms and are tricky to diagnose.
Current testing relies on PCR tests that look at one gene at a time. This results in a prolonged diagnosis, or – often – underdiagnosis, especially in children without a family history of the disorders.
This study is one of the first to show that whole genome sequencing can be used for repeat expansion disorders. “Here in a single test, we have the capacity to diagnose the most common neurological diseases,” said one of the study authors, Sir Mark Caulfield, in the Guardian Newspaper.
What did the study do?
The study first investigated the effectiveness of whole genome sequencing in detecting repeat expansion disorders using samples from over 400 patients previously tested by PCR in the UK’s National Health Service. The researchers found that whole genome sequencing was as accurate and sensitive as PCR testing in detecting repeat expansion disorders.
Then the researchers used whole genome sequencing on samples from over 11,000 undiagnosed people who had clinical features consistent with a repeat expansion disorder and who took part in the 100,000 Genomes Project. They then used an algorithm designed to detect repeat expansions from whole genome sequencing. Their approach led to the diagnosis of over 60 patients, including children with intellectual disabilities who did not have a family history of repeat expansion disorders, and an adult with Friedreich’s ataxia.
What next?
The study makes the case for whole genome sequencing to be used as a routine diagnostic test in people suspected to have a neurological repeat expansion disorder. Such a diagnosis would be much quicker and more efficient for patients.
“It is very exciting because it opens up the vista of a test that could end the diagnostic odyssey for many patients,” said Sir Mark.
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