Diagnosis of a genetic cause in hundreds of people with motor neuron disease could be missed due to 'arbitrary age limits and rules' on genetic testing

The research estimates that although nearly a quarter of people with ALS who do not have family members with the illness do have a genetic link to their ALS, this link goes undetected in 98% of cases because of current guidelines. As a result, they are not offered proper genetic advice and counselling, and would not be able to access gene-based therapies likely to be available soon or in trials. The researchers say that genetic testing should be open to all patients with ALS, regardless of whether or not other family members are affected, and for all ages.

ALS is a progressive nervous system disease that affects nerve cells in the brain and spinal cord, causing paralysis of muscles. Around 1 in 300 people will be diagnosed with ALS at some point in their lives, with the average person surviving for between two and five years after their symptoms begin. There is currently no cure for ALS.

In some cases, there is an identifiable genetic cause. Given the current restrictive testing guidelines, the researchers wanted to establish the probability of a positive genetic test result in various scenarios to provide evidence for how and when genetic testing should be used. They performed two analyses on global data sets, analysing the four most common ALS genes and a larger panel of 26 ALS genes.

Their analysis revealed that, by limiting testing in those without a family history to people with symptom onset below 40 years, as per current UK guidelines, 115 of 117 positive test results were missed. Extrapolating this data to other health systems across the world, they found that potentially thousands of people with ALS will not know they have a genetic cause of their ALS due to the inaccessibility of testing.

Professor Ammar Al-Chalabi, Professor of Neurology and Complex Disease Genetics at King's IoPPN, and the study's lead author, said, "ALS is a condition that destroys lives. Genetic testing means that people and their families can be given correct advice and access to genetic counselling and be supported with family planning. Our study found that there are large numbers of people who are unable to access this care and support because of the arbitrary age limits and rules currently in place."

While the researchers recognise that expanding the guidelines to include more people will be resource intensive, they argue that, where possible, countries should aim to offer genetic testing to ALS patients of all ages.

Dr Puja Mehta, the study's first author, said "Our study shows the importance of being able to offer people with ALS of all ages a blood test to identify a possible genetic cause. In addition to accessing appropriate genetic counselling and support, with the exciting prospect of specific gene-based therapies on the horizon, and with clinical trials underway, it will become all the more important for people with ALS to know if they have an identifiable genetic cause."

Dr Nicholas Cole, Head of Research at the MND Association said: "This research, supported by the MND Association, adds weight to the suggestion that routine genetic testing should be offered to MND patients, regardless of their age at onset or family history of the disease. Genetic testing could provide opportunity for more people with MND to be involved in tailored clinical trials. However, it is imperative that testing is supported by a robust genetic counselling infrastructure to provide tailored support to all those who choose to embark upon this process.

"These findings are thanks to the people with MND who have generously contributed to datasets funded by the MND Association, including ProjectMinE, the UK National DNA Bank for MND Research and the MND Register for England, Wales and Northern Ireland, each of which is accelerating the global effort to find treatments, and eventually a cure for MND.

"Together with our researchers, their support means we are understanding more about this complex disease and helping to focus effort and expertise in the right areas."

This research was part-funded by the National Institute for Health and Care Research (NIHR) Maudsley Biomedical Research Centre.