Research led by scientists at UCL have identified the first blood test able to predict the onset and progression of Huntington’s disease (HD).

The findings, which have been published in Lancet Neurology, should help test new treatments for the incurable, fatal genetic brain disorder, the researches note.

“This is the first time a potential blood biomarker has been identified to track Huntington’s disease so strongly,” said the study’s senior author, Dr Edward Wild, UCL Institute of Neurology.

The test measures levels of a particular protein (neurofilament) released from damaged brain cells, which has previously been linked to other neurodegenerative diseases but until now hadn’t been assessed in Huntington’s disease.

The team found that levels of the brain protein were increased throughout the course of HD even in carriers of the HD genetic mutation who were many years from showing symptoms of the disease.

In fact, HD mutation carriers had neurofilament concentrations that were 2.6 times that of the control participants, and the level rose throughout the disease course from premanifest to stage 2 disease.

In participants who had no symptoms at the start of the study the level of neurofilament predicted subsequent disease onset, as those with high levels were more likely to develop symptoms in the following three years, the researchers said.

Even taking into account factors already known to predict progression - age and a genetic marker - neurofilamant levels could still independently forecast onset, progression and the rate of brain shrinkage, they noted.

"We have been trying to identify blood biomarkers to help track the progression of HD for well over a decade, and this is the best candidate that we have seen so far," said Dr Wild.

"Neurofilament has the potential to serve as a speedometer in Huntington's disease, since a single blood test reflects how quickly the brain is changing. That could be very helpful right now as we are testing a new generation of so-called 'gene silencing' drugs that we hope will put the brakes on the condition. Measuring neurofilament levels could help us figure out whether those brakes are working.”

However, “more work is needed to understand the potential and limitations of this test," cautioned study author Lauren Byrne, also from the UCL Institute of Neurology.

“In the future, if drugs to slow HD become available, it may well be used to guide treatment decisions. For now, this test is most promising as a much-needed tool to help us design and run clinical trials of new drugs.”