A new blood-based test that could help speed up diagnoses for children born with rare genetic disorders has been developed by researchers in an effort to provide answers – and treatments – sooner.
Rare genetic disorders include a host of conditions, from cystic fibrosis to diseases relating to the mitochondria – the powerhouses of our cells. However, getting a diagnosis can be arduous.
“In most cases people suspected of a rare disease undergo genomic testing, which revolutionised their diagnosis, but typically only leads to a diagnosis about 50% of the time,” said Dr David Stroud, the co-author of the study from the University of Melbourne.
“Those that don’t receive a diagnosis from genomic testing often undergo a long ‘diagnostic odyssey’ of months to years where they undergo myriad other tests in an effort to interpret which of the many genetic changes detected in genomic testing are causing the disease,” he added. “Some of these tests are very invasive, needing for example muscle biopsies, which in children requires general aesthetic, which has its own risks.”
Writing in the journal Genome Medicine, Stroud and colleagues report how they sought to supplement genetic testing with another approach: examining the myriad proteins found within certain types of blood cells taken from a patient, and comparing them against those found in healthy people.
“Since genes are the instructions to make proteins, we then use this information to understand which of the thousands of changes in many different genes detected in a patient are leading to a damaged protein and which are benign,” said Stroud.
The team say the approach means the effects of many different genetic mutations can be analysed at once and yield results in as little as three days.
Among other results the researchers found the new approach outperformed current gold-standard tests for mitochondrial diseases that are used alongside genetic testing, and enabled the diagnosis of diseases where genomic testing alone had been unable to do so.
“Genomics is the frontline test and it can solve the diagnosis in about 30-50% of patients suspected of a rare disease. We think a single proteomic test can increase that diagnostic yield to 50-70% of suspected patients,” said Prof David Thorburn, another author of the research from the University of Melbourne.
While the study focuses on using the test for mitochondrial diseases, Stroud said it was already applicable to about half of the 7,000 known rare diseases, although more work was needed to demonstrate this.
Stroud added that for mitochondrial diseases as little as 1ml of blood from a newborn was required for the procedure, whereas current techniques involved a muscle biopsy.
Furthermore, while a mitochondria-focused version of the test has a similar cost to current techniques, it is not specific to one kind of rare disease. That not only makes it more cost-effective but, as Stroud noted, it also means patients could avoid having to take other unnecessary tests.
“This has obvious benefits to both the patient and healthcare system,” he said.
A diagnosis not only sheds light on the disease, and – in some cases – possible treatments. It also helps parents who are considering having further children by raising the possibility of pre-natal genetic testing.
Michal Minczuk, a professor of mitochondrial genetics, at theUniversity of Cambridge, and who was not involved in the study, welcomed the research. “Overall, the paper marks a very significant step forward in diagnostic practices by introducing a robust, rapid, and minimally invasive method for confirming and characterising genetic disorders,” he said. “This could greatly enhance patient care by expanding the tools available for clinicians and researchers in genomic medicine.”
Robert Pitceathly, a professor of clinical neurology and mitochondrial medicine at UCL Queen Square Institute of Neurology, agreed. “The next step is broader validation and integrating this technology into NHS diagnostic services to improve patient outcomes,” he said.