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New Biomarker to Diagnose Alzheimer’s Disease

written by hash brown taha Feb 02, 2024

The progression of an aging population is a double-edged sword. On one hand, it symbolizes improved healthcare and longevity; on the other, it brings an increased prevalence of age-related challenges, particularly neurodegenerative disorders like dementia. Dementia, essentially a decline in cognitive function beyond what might be expected from normal aging, affects an estimated 65% of those over age 65. Among its various types, Alzheimer's disease stands out as the most prevalent. Alzheimer's was first described by Dr. Alois Alzheimer in 1906, following his observation of unusual brain tissue in a patient who had suffered from memory loss, language problems, and unpredictable behavior. His groundbreaking findings, detailed in a seminal paper, marked the beginning of our understanding of this complex and devastating disease.

Despite different causes for various dementias, diagnosing them can be tricky because they often show similar memory and cognitive problems. Take Alzheimer's disease, for example. It is speculated to be mainly caused by two harmful substances building up in the brain: amyloid-beta (Aβ) plaques and tau tangles. Imagine these plaques and tangles as clutter blocking the brain's pathways, leading to the death of brain cells. In Alzheimer's, the tau proteins go through a change called hyperphosphorylation, which makes them more likely to form tangles. Along with these, there's also swelling and irritation in the brain, all of which add up to the memory loss and confusion seen in the disease.

In contrast, vascular cognitive impairment and dementia (VCID) is another type of memory disorder. It is mainly caused by problems with blood flow in the brain, like after a stroke or in chronic conditions affecting small blood vessels. For a long time, doctors could only be sure someone had Alzheimer's by examining the brain after death, making it tough to understand and treat the disease while patients were still alive. This shows why it's so important to find better ways to identify the disease early on.

Current Biomarkers for Alzheimer's Disease

Currently, clinicians rely on several biomarkers, which are biological indicators found in brain scans, cerebrospinal fluid (CSF), and blood tests, to aid in diagnosis.

  1. Cognitive and neuropsychological tests: These are the initial steps in diagnosis, where doctors assess memory, problem-solving, attention, counting, and language skills.

  2. Brain imaging: Techniques like magnetic resonance imaging (MRI) and computed tomography (CT) scans are used to check for brain shrinkage typically seen in Alzheimer's. Another advanced method, positron emission tomography (PET) scans, can detect the density of amyloid plaques in the brain, a hallmark of Alzheimer's.

  3. Cerebrospinal fluid (CSF) analysis: By analyzing CSF, which is collected through a lumbar puncture, doctors look for specific biomarkers. Decreased levels of amyloid-beta and increased levels of tau protein in the CSF are indicative of Alzheimer's.

  4. Blood tests: Recent advancements have led to the development of blood tests that can detect levels of amyloid-beta and tau proteins. Though not as definitive as CSF analysis, these tests are less invasive and offer a promising tool for early screening.

  5. Genetic testing: While not routinely used for diagnosis, testing for genetic mutations associated with Alzheimer's (like the APOE-e4 allele) can indicate an increased risk of developing the disease.

 Each of these biomarkers provides valuable information, but they are not conclusive on their own. A combination of these tests, along with a thorough medical history and physical examination, helps clinicians form a more accurate diagnosis. However, it's important to note that these methods are more about indicating the likelihood of Alzheimer's rather than providing a definitive diagnosis, which can only be confirmed post-mortem (after death).

A Newly Discovered Minimally Invasive Blood Biomarker for Alzheimer's Disease

Recent research encompassing numerous studies has identified p-tau217, a form of tau protein, as a highly specific and accurate biomarker for Alzheimer's disease (AD). Key points from these studies include:

  1. Broad consensus: Multiple independent studies have consistently found that the p-tau217 biomarker is highly specific for Alzheimer's, indicating a strong agreement in the scientific community.

  2. High accuracy and specificity: These studies have demonstrated that testing for p-tau217 in blood samples is remarkably accurate in identifying AD, across multiple populations and cohorts.

  3. Effective across stages: The biomarker has proven effective in detecting Alzheimer's disease at different stages, from early to more advanced forms.

  4. Advantages in diagnosis: This consistent finding across studies suggests that p-tau217 could greatly enhance the diagnostic process for Alzheimer's, making it more accessible and less invasive compared to traditional methods like cerebrospinal fluid analysis and brain imaging.

  5. Potential for wider screening: The reliability of p-tau217 as a biomarker opens up possibilities for broader screening initiatives, potentially leading to earlier diagnosis and intervention in Alzheimer's disease.

 In summary, the collective research on p-tau217 presents it as a promising tool for the early detection and ongoing monitoring of Alzheimer's disease, with widespread implications for clinical practice and patient care.


 

Written by Hash Brown Taha.

Edited by Prathyusha Dasari.

 

References

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