Scientists are making great strides in developing a blood test to detect Alzheimer’s years before symptoms first appear.

But Alzheimer’s isn’t the only type of dementia, and there are many other kinds of neurodegenerative diseases and brain disorders where early diagnosis would be just as valuable.

Now, for the first time, scientists say they’ve developed a blood test that can identify different types of brain disorders in the earliest of stages.

It’s all because of a recently discovered compound that’s linked to Alzheimer’s disease called neurofilament light (NfL).

We first reported on NfL last January when researchers at Lund University in Sweden began studying this protein’s connection to Alzheimer’s disease. Researchers found that NfL is highly expressed in nerve fibers and is linked to a wide range of neurological diseases.

Many brain disorders result in irreversible damage to nerve fibers within the brain. When this damage happens, NfL is released.

Now, Lund researchers say they’ve proven that testing NfL levels in the blood can diagnose dementia, among other neurological diseases.

Distinguished Between Different Forms of Parkinson’s 

Scientists at Lund University and King’s College London examined 3,138 blood samples from men and women who were either cognitively unimpaired, were diagnosed with depression, had Down syndrome or suffered from one of 13 neurodegenerative disorders.

The results showed concentrations of NfL in blood were higher across all neurodegenerative disorders when compared to the blood of the cognitively healthy.

The highest readings were in those with Down syndrome dementia, amyotrophic lateral sclerosis (ALS) – also known as Lou Gehrig’s disease – and frontotemporal dementia (FTD).

Although the test is not able to distinguish between different disorders, it did provide valuable insight into some of them.

For instance, an NfL blood test was able to distinguish atypical Parkinsonism from Parkinson’s disease with very high diagnostic accuracy. These are different disorders but because they have similar symptoms they are sometimes misdiagnosed.

What’s more, while FTD with its unusual behavior and loss of speech or language as initial symptoms can present a diagnostic challenge, the test could identify these patients, differentiating them from those with other forms of cognitive impairment.

The test was also able to distinguish neurodegenerative disorders from depression in older adults, another valuable insight enabling doctors to provide the patient with proper treatment.

A Rapid Screening Tool 

Not surprisingly, the test is ultra-sensitive. This is because, among other things, NfL is also found in the blood of healthy people. In fact, as you get older more NfL is released, doubling between the ages of 20 and 50, and further doubling by age 70.

One of the study’s leading authors, Dr. Abdul Hye, said, “For the first time we have shown across a number of disorders that a single biomarker can indicate the presence of underlying neurodegeneration with excellent accuracy.

“Though it is not specific for any one disorder, it could help in services such as memory clinics as a rapid screening tool to identify whether memory, thinking or psychiatric problems are a result of neurodegeneration.”

Another study author, Professor Oskar Hansson, added, “Blood tests have great potential to improve the diagnosis of dementia both in specialized memory clinics and in primary care.

“Plasma NfL can be extremely useful in a number of clinical scenarios which can greatly inform doctors, as shown in this large study.”

Already Available in Some Countries 

The researchers believe that NfL could be one of the biological markers that will finally lead to cheap, accurate, painless and accessible tests with the ability to detect biological processes that will develop into future brain diseases if left untreated.

One day these tests could replace less satisfactory diagnostic methods that are currently available including invasive spinal tap procedures, expensive brain scans, and unreliable cognitive tests.

In some European countries, such as Sweden and The Netherlands, the NfL test is already being utilized as a routine assessment tool for diagnosing brain disorders. Hopefully it will become available here soon.


  1. https://www.kcl.ac.uk/news/simple-blood-test-can-accurately-reveal-underlying-neurodegeneration
  2. https://www.nature.com/articles/s41467-021-23620-z 

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