A new test for over 50 genetic diseases should cut diagnosis from decades to days. 

The new DNA test can identify a range of hard-to-diagnose neurological and neuromuscular genetic diseases quicker and more-accurately than existing tests.

It was developed by researchers at the Garvan Institute of Medical Research in Sydney and collaborators from Australia, UK and Israel. 

“We correctly diagnosed all patients with conditions that were already known, including Huntington’s disease, fragile X syndrome, hereditary cerebellar ataxias, myotonic dystrophies, myoclonic epilepsies, motor neuron disease and more,” says Dr Ira Deveson, Head of Genomics Technologies at the Garvan Institute.

The diseases covered by the test belong to a class of over 50 diseases caused by unusually-long repetitive DNA sequences in a person’s genes – known as ‘Short Tandem Repeat (STR) expansion disorders’.

“They are often difficult to diagnose due to the complex symptoms that patients present with, the challenging nature of these repetitive sequences, and limitations of existing genetic testing methods,” says Dr Deveson.

A new study published in Science Advances shows that the test is accurate, and allows the team to begin validations to make the test available in pathology services around the world.

Using a single DNA sample, usually extracted from blood, the test works by scanning a patient’s genome using a technology called Nanopore sequencing.

“We’ve programmed the Nanopore device to hone in on the roughly 40 genes known to be involved in these disorders and to read through the long, repeated DNA sequences that cause disease,” says fellow researcher Dr Kishore Kumar.

“By unravelling the two strands of DNA and reading the repeated letter sequences (combinations of A, T, G or C), we can scan for abnormally long repeats within the patient’s genes, which are the hallmarks of disease.

“In the one test, we can search for every known disease-causing repeat expansion sequence, and potentially discover novel sequences likely to be involved in diseases that have not yet been described,” says Dr Deveson.

The Nanopore technology used in the test is smaller and cheaper than standard tests, which the team hopes will smooth its uptake into pathology labs. 

“With Nanopore, the gene sequencing device has been reduced from the size of a fridge to the size of a stapler, and costs around $1000, compared with hundreds of thousands needed for mainstream DNA sequencing technologies,” says Dr Deveson.