How a new blood may help detect neurodegenerative diseases

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Blood tests may help detect some neurodegenerative diseases in the future. Patricio Nahuelhual/Getty Images
  • Researchers have discovered a blood marker they say can help in diagnosing certain neurodegenerative diseases.
  • Many neurodegenerative diseases, such as ALS, are diagnosed by ruling out other diseases as the cause of a person’s symptoms.
  • Medical professionals often cannot definitively diagnose many of these disorders until after the person has died.

Researchers say they have found a blood marker that could help in identifying and diagnosing three neurodegenerative diseases – frontotemporal dementia (FTD), amyotrophic lateral sclerosis (ALS), and progressive supranuclear palsy (PSP).

They have published their findings in the journal Nature Medicine.

The researchers noted how each of the neurodegenerative diseases operates:

  • FTD results from damage to neurons in the frontal and temporal lobes of the brain.
  • ALS, also known as Lou Gehrig’s disease, affects motor neurons and nerve cells in the brain and spinal cord that control voluntary muscle movement and breathing.
  • PSP is caused by nerve damage in nerve cells that affect walking, balance, and eye function. It is an atypical parkinsonism disorder, but it progresses more quickly than Parkinson’s disease.

The study included 991 participants, some of whom were affected by one of the three diseases and others who belonged to a control group of healthy individuals.

Each of these diseases can be characterized by serious health issues, including but not limited to dementia, behavioral symptoms, paralysis, muscle wasting, and movement impairments. While these conditions are relatively rare, they can be debilitating or fatal to those living with them.

The new blood test involved determining levels of proteins called tau and TDP-43 in vesicles, which are tiny lipid (fat) sacs that can enter into the bloodstream. The test is not ready yet for routine medical use, but experts say it shows great promise.

“[It is] fascinating to read about a possible new neurology blood test that is novel and looking for tau-proteins inside of vesicles,” Dr. Clifford Segil, a neurologist at Providence Saint John’s Health Center in California who was not involved in the study, told Medical News Today. “Though this lab test is a new way to look at tau levels in patients’ blood it is challenging to assign what disease abnormal tau levels cause clinically.”

“These rare diseases cause severe disability and due to being uncommon there are often delays in these diagnoses,” Segil said. “In my opinion, their clinical pictures are very different, and a clinical neurologist should be able to isolate the symptoms and then send a patient to a dedicated neuromuscular neurologist to confirm a general neurologist’s suspicion for ALS, and similarly to a movement disorder neurologist to confirm the suspicion for PSP and to a cognitive behavioral neurologist to confirm the suspicion for FTD.”

The authors note that it is difficult to definitively diagnose a person with a neurodegenerative disease during their lifetime because brain tissue must be examined for tau and TDP-43 proteins, which might play a role in all three. For FTS, there needs to be a combination of both. For ALS, the presence of TDP-43 is enough. For PSP, the presence of tau protein is sufficient.

“Currently we use clinical presentation, family history, genetic testing, and imaging biomarkers to currently diagnose these diseases,” said Dr. Shae Datta, a clinical assistant professor in the Department of Neurology at NYU Long Island School of Medicine in New York.

“They can be hard [to] diagnose because the symptoms are similar to those of other conditions,” Datta, who was not involved in the study, told Medical News Today. “The behavioral variant of FTD is sometimes misdiagnosed as a mood disorder like depression. It can also be common to have FTD and another type of dementia, such as Alzheimer’s disease.”

“I think whenever new biomarkers are available, it can help us clinically diagnose a patient more accurately than more expensive invasive testing,” she added.

Experts say the discovery of blood markers (also called biomarkers) could enable medical professionals to make an accurate diagnosis while someone is still alive.

Right now, diagnosis of these illnesses includes eliminating other causes of the symptoms.

“This [blood test] may help us with earlier diagnosis in some patients where the presentation is not clear,” Datta said. “It seems that the level of certain proteins detected could suggest a higher disease burden in these patients. Currently, we do not have any disease-modifying therapies for these conditions, but this could help us group patients better in terms of chronicity when there are available treatments.”

Blood biomarkers probably aren’t going to replace a clinical diagnosis, Segil pointed out.

“I do not believe a biomarker of blood test will replace a clinical neurologist diagnosis of FTD, PSP or ALS as these are life changing rare neurological diagnoses,” he said. “As a clinical neurologist I think blood tests like this proposed tau-vesicle test may be used in addition to a detailed neurological exam from a clinical neurologist. In neurology a good clinical exam often is more valuable than blood tests. As a neurologist my job is to rule out the obvious and sneaky so blood tests will always be an important part of my neurology evaluation and I am excited to see if tau-vesicle lab tests prove to have clinical benefits in the future.”

Biomarkers don’t just help with early diagnosis. They can also provide valuable information during treatment.

“The biggest takeaway is that this is the first biomarker that enables the identification of underlying disease pathology in ALS, FTD, and PSP,” Anja Schneider, a translational dementia researcher in Germany and the lead author of the study, told Medical News Today. “It is also the first diagnostic fluid biomarker for these diseases.”

“In FTD, there are drug candidates directed against tau or TDP pathology,” Schneider explained. “However, it has not been possible to test these therapies in clinical trials because there was no biomarker available to inform whether a patient has underlying Tau or TDP pathology (with the exception of very rare genetic cases where the mutation informs about the associated molecular pathology. However, therapy trials in genetic FTD are not feasible because these cases are really rare).”

“With the new marker, we may be able to stratify FTD patients to trials and hopefully therapy,” she added. “Both biomarkers bear the potential to reflect treatment response in therapy trials and may thus serve as an outcome parameter.”

The discovery of the biomarker can be a game-changer, noted Jennifer Bramen, PhD, a senior research scientist and director of neuroimaging at the Pacific Neuroscience Institute in California who was not involved in the study.

“A blood test that can quickly and accurately subtype neurological diseases will improve patient care and accelerate research,” she told Medical News Today.

Bramen added that the discovery of biomarkers can help with early diagnosis and effective treatments and might improve quality of life.

Read the full article here

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