New technology has allowed geneticists to use a single blood test to screen a person’s entire DNA to diagnose learning disabilities, it has been revealed.

Speaking at the 8th FENS Forum of Neuroscience, Europe’s largest neuroscience conference in Barcelona today (17 July), Dr Joris Veltman from Radboud University Nijmegen Medical Center in the Netherlands described the first results of a single blood test to screen a person’s entire DNA to diagnose genetic brain disorders.Dr Veltman and his colleagues have been investigating gene mutations that cause learning disabilities for decades. Any of around 1,000 genes could be involved so the diagnostic ability of most existing tests based on single gene analysis is low, time-consuming and expensive.

The new blood test, known as whole exome sequencing, is set to revolutionise clinical care of people with — or carriers of — genetic disorders.For instance, it could mean that children are diagnosed with a learning disability at an earlier stage.

“Parents bring their child into the clinic because they know that the child is not developing properly. Being able to diagnose the disorder and the cause of it is extremely important for how the family will manage the situation. Even if there is little or no treatment, the parents need to know about how their child will develop, what they can expect, what the cause is and what the chance is that a second child will also develop the disorder,” said Dr Veltman.

Following this, Dr Veltman and his team have now embarked on studies of common forms of learning disability. In a pilot study they identified diagnostically relevant gene mutations in 3 out of 10 patients with unexplained intellectual disability.“In these initial studies, we were able to identify the cause and the specific mutation in more than 20% of the patients. This represents a major improvement of the diagnostic yield in this group of patients. Most of these mutations are not present in the DNA of the parents but occur for the first time in the germline of the patients that the child inherits. These studies help us not only to diagnose patients but also to identify novel genes for learning disability. Identifying the biological origin of learning disability can also help us develop new therapies in the future,” he said.

Dr Veltman believes the majority of disease genes causing learning disabilities will be identified by exome sequencing approaches within the next few years.“Whole exome sequencing simplifies previous test for genetic disorders. An early diagnosis will help parents cope with their child’s disability and plan for the future, and gives new hopes for therapy development.”