Promise of blood test to predict course of Huntington's disease

Scientists have identified the first promising biomarker for Huntington's disease (HD) that could be harnessed in a simple blood test to predict disease onset and progression.

The blood test would measure levels of neurofilament, a protein released by damaged brain cells. The researchers found neurofilament levels increase as HD progresses, but can also be detected in the blood years before symptoms manifest.

'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 senior author Dr Edward Wild at University College London (UCL), UK. '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.'

Huntington's disease is an incurable, autosomal dominant genetic disease where patients suffer from a progressive decline of motor and cognitive function, including involuntary movements, personality changes and worsening dementia. The disease is caused by a mutation in the huntingtin gene, which causes brain cell death. Most HD carriers start to show symptoms in their 30s to 50s.

Previous research had linked concentration of neurofilament in the blood of patients with other neurodegenerative disorders, but until now neurofilament had only been measured in the cerebrospinal fluid of HD patients.

The researchers used data from the international TRACK-HD study, which gathered data using blood tests, brain scans and tests of cognitive and motor skills from 366 HD carriers and control volunteers over three years.

By comparing 201 HD carriers with 100 controls, the researchers found patients with the HD mutation had as much as three to six times higher levels of neurofilament in their blood compared with controls. Neurofilament could also be detected in HD carriers who were years away from showing symptoms.

'This is the first time neurofilament has been measured in blood, so much more work is needed to understand the potential and limitations of this test,' said lead author Lauren Byrne from UCL's 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.'

The authors believe neurofilament may also have potential as a biomarker in the preclinical phases of other neurodegenerative diseases.

About 12 in 100,000 people in the UK are affected by HD and children have a 50 percent chance of inheriting the disorder. Gene tests, age and measures of brain volume have been the best predictors of HD until now.

The study was published in the Lancet Neurology.