Brain Sciences


Blood test could detect Alzheimer’s years before symptoms appear

27 June 2019

The first signs of Alzheimer’s disease could be detected 15 years before symptoms develop with a single blood test, finds a new UCL-led study.

Blood sample

Researchers were trying out a test for neurofilament light protein (NfL) in blood serum samples from 61 people, 46 of whom were genetically predisposed to Alzheimer’s disease.

With the 46 people who carry the mutation causing familial Alzheimer’s disease, the researchers were able to predict how many years they were away from onset, based on their parents’ histories.

The new study, from the UCL Dementia Research Centre (Queen Square Institute of Neurology), published in Alzheimer’s Research & Therapy, found that levels of NfL, which is a product of nerve cell damage, were higher in mutation carriers 15 years prior to the expected onset of symptoms, with NfL levels continuing to progressively increase thereafter.

The study’s lead author, Dr Philip Weston, said: “The findings of the study, while requiring further replication, suggest that the use of a blood test for neurofilament light could prove to be a powerful tool in identifying those most at risk of developing cognitive symptoms due to Alzheimer’s, and also in tracking early changes progressively over time.”

The most common symptom of Alzheimer’s disease is progressively worsening memory for recent events, causing individuals affected to become progressively more forgetful. Over time other aspects of cognition including language, planning, judgement and visual processing are also affected, causing those affected to become progressively more dependent on those around them.

“The possibility of using a simple blood test to detect such early changes is likely to be very valuable, especially as blood tests are generally more widely available, cheaper and less invasive than other methods for measuring change such as doing brain scans or lumbar punctures,” said Dr Weston.

The researchers are hoping that NfL could be used in research, to assess how well drugs are working in clinical trials, and to select participants for those trials. With further research to make a blood test more specific to Alzheimer’s, NfL testing may one day be part of a screening test for people with concerns about their memory – if NfL levels are high, more costly tests could be warranted.

Research teams are also investigating tests for amyloid beta, one of the brain proteins understood to cause Alzheimer’s. Alone, amyloid beta is not sufficient to cause symptomatic Alzheimer’s – so NfL is used as a marker of neuronal loss.



  • Source: National Eye Institute on Flickr