can a blood test for Alzheimer's disease provide clues for a cure?

Alzheimer’s disease, the most common type of dementia, causes cognitive decline, mood and behavior changes, and memory loss. The leading cause of Alzheimer's disease (AD) is the accumulation of the 42-amino-acid-long amyloid beta-peptide, the Aβ1–42 in the brain. Research shows that patients with AD have less Aβ1–42 in their cerebrospinal fluid (CSF) than healthy individuals. 

Advancements in CSF detection and positron emission tomography (PET) analyses have improved accuracy in diagnostic processes. This enables researchers to detect Alzheimer's earlier. A drawback to the PET process, however, is that it is very involved and costly, and not always accessible to everyone — PET scans are only available in specific medical centers in wealthy countries.

Sampling and screening of cerebrospinal fluid (CSF) seems to be a cheaper diagnostic approach, but the procedure can lead to complications, such as headaches. Also, CSF is not a standard procedure in many clinics around the world.

Alzheimer's Biomarkers in Blood

Researchers have begun using blood testing for Alzheimer studies. Recent advances in detection technologies and serology studies enable scientists to better detect circulating biomarkers (RNAs, proteins, and other molecules) in the blood, leading to more precise and reliable measurements of diseases. Blood tests also enable researchers to screen large numbers of healthy people in an effort to identify those most likely to develop AD. 

If successful, blood tests that detect circulating biomarkers of AD can help researchers develop therapeutic medications that are designed to be administered before the onset of AD symptoms. It is hoped that such medications can delay cognitive symptoms by at least five years. Multiple labs worldwide have been looking for new biomarkers for AD. They are developing blood tests that can identify the early signs of Alzheimer’s disease, monitor the disease progression, and differentiate it from similar conditions.

Here are some of the new biomarkers discovered so far:

Biomarker: aβ42 and aβ40: The presence of aβ42 and aβ40 isoforms show a buildup of amyloid plaques in the brain, which triggers a sequence of pathological processes. Lower ratios of aβ42:aβ40 and levels of aβ42 in the cerebrospinal fluid are the best indicators of Alzheimer’s Disease.

Biomarker: Neurofilament Light: A recent study shows patients with Alzheimer’s experience an increase in neurofilament light (Nfl) chain protein in the spinal fluid and the blood 16 years before onset. The study also found the rate of increase in the protein correlated with the shrinking of the brain’s precuneus region, and the patients performed worse in cognitive tests. The protein makes a reliable biomarker to track the progression of the disease non-invasively.

Biomarker: Tau and p-tau: Studies presented at the 2020 Alzheimer’s Association International Conference showed the tau protein p-tau217 is an indication of the presence of Alzheimer’s disease. High levels of tau or the phosphorylated form, p-tau, make a reliable biomarker candidate because it also indicates the presence of damaging neurofibrillary tangles in the brain. According to another Alzheimer’s researcher, Dr. Michael Weiner at the University of California, San Francisco (UCSF), this blood test accurately predicts the presence of the disease in the brain.

Is there a blood test available today that accurately identifies Alzheimer’s disease?

To date, there’s no specific blood test for Alzheimer’s. However, the identification of these biomarker candidates can help researchers get closer to accurately predicting or identifying the presence of the disease in patients through blood collection and blood testing.

Advances in blood collection methods make it easier for researchers to engage a wider group of participants in AD clinical trials. Venous blood draws in a clinic are not necessary as a standard blood collection method. Instead, researchers can use remote sample collection methods that are less invasive and more convenient for participants. Remote blood collection can eliminate the need for clinic visits, thus enabling virtual clinical trials.

The development of remote blood collection tools such as the Mitra^® device based on VAMS^® technology means that more people – in this case, people who suspect they have a predilection for Alzheimer's disease – can remotely participate in clinical research studies, virtual clinical trials and telemedicine programs. In most cases, they can collect their own blood samples at home and mail them to the designated microsampling lab for analysis.

This is curated content. To learn more about the research behind this news update, please view the original source materials included here:

https://www.the-scientist.com/features/the-hunt-for-a-blood-test-for-alzheimers-disease-66743  
https://www.the-scientist.com/news-opinion/protein-changes-detected-in-blood-years-before-alzheimers-onset-65347  
https://www.the-scientist.com/infographics/infographic--biomarkers-in-blood-provide-a-window-into-the-brain-66749 
https://www.the-scientist.com/news-opinion/experimental-blood-test-could-flag-alzheimers-67779  

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