Inherited neurological disorders normally require multiple tests, meaning it can take years for patients to obtain a definitive diagnosis. However, new research suggests a simple DNA test, known as whole genome sequencing (WGS), can quickly and accurately detect the most common inherited neurological disorders.
A study led by Queen Mary University of London, Illumina, UCL and Genomics England, in conjunction with NHS England, evaluated the role of WGS in the commonest causes of inherited neurological diseases, such as Fragile X syndrome (intellectual disability), Huntington’s disease, Friedreich's ataxia and some forms of amyotrophic lateral sclerosis (ALS) and frontal lobe – or frontotemporal – dementia.
Nearly 70 people benefited from receiving a new diagnosis
The study compared the accuracy of WGS compared to the test currently in use (PCR tests) by detecting repeat expansion disorders in 404 patients. From the results, they concluded that the accuracy and sensitivity of the WGS test was comparable to the PCR test.
The researchers then used WGS from more than 11,600 undiagnosed people who had clinical features associated with a repeat expansion disorder who are participants in the 100,000 Genomes Project.
In total, 68 people received a new diagnosis, among those was a 10-year-old girl with an intellectual disability and an 18-year-old with dementia.
The new test provides results quicker than the standard NHS test
WGS was found to provide results quicker and more efficiently compared to the standard NHS test which only looks at one gene at a time. This means patients with undiagnosed conditions usually have to take multiple tests over many months or years – a time-consuming process that results in the underdiagnosis of people who have atypical clinical presentations.
One patient who was diagnosed with Friedreich's ataxia through the study, said she is “grateful” the study has allowed her to have a definitive diagnosis, that otherwise would have taken many years to be made, if at all.
She said: “Having a diagnosis isn’t a cure, but at last I knew what was happening and to understand what I needed to do to delay the inevitable for as long as possible.”
The findings “support whole genome sequencing within the NHS”
The researchers say the findings support WGS for use within the NHS to diagnose patients whose doctors believe may have a repeat expansion disorder.
Professor Dame Sue Hill, Chief Scientific Officer for England, said: “This research demonstrated the power of whole genome sequencing in helping to detect common neurological conditions and how it can lead to faster and more accurate diagnoses.
“We are already seeing the benefit of WGS in a clinical setting through the NHS Genomic Medicine Service and this research further proves the benefits of this kind of testing.”