A New Blood Test Could Detect Early Symptoms of Alzheimer’s

Blood Test Detect Early Symptoms of Alzheimer’s

Currently, there is no single, simple diagnostic test for Alzheimer’s. Developing a straightforward, non-invasive, and inexpensive early diagnostic test could aid in early diagnosis and the targeting of new Alzheimer’s medications to those in the early stages of the disease. Recently, a team of researchers has discovered a blood test that detects a specific type of tau protein. This test can potentially help identify changes in amyloid and tau in the brain.

Researchers have discovered a novel, potentially useful diagnostic tool for early Alzheimer’s diagnosis that provides a non-invasive, commercially feasible method for early illness detection in clinical settings.

According to a new study published in JAMA Neurology, a blood test used to screen for Alzheimer’s shows promise in identifying changes in brain levels of tau and amyloid beta proteins years before symptoms develop [1].

Even though Alzheimer’s affects over 55 million people globally, there is no reliable and straightforward method for diagnosing the disorder [2]. According to the Centers for Disease Control and Prevention (CDC), this has resulted in a situation where less than half of dementia patients in the US have a medical diagnosis [3].

When diagnosing dementia, doctors typically take a patient’s medical history, rule out other dementia kinds (such as vascular dementia), and perform testing on the cerebrospinal fluid or scans. All of these are costly, time-consuming, and even invasive.

Identifying the disease in its early stages is challenging when testing is inaccurate. As a result, the few treatment options available for Alzheimer’s cannot be initiated early (when they may be most beneficial), and it is also difficult to design trials to establish whether certain medications might be effective if taken early in the disease.

Can a blood test for Alzheimer’s aid in an early diagnosis?

Scientists have been searching for a simple blood or saliva test to identify if an individual has the typical build-up of tau and amyloid beta in their brain. The blood-brain barrier restricts the quantity of substances present in the brain from entering the bloodstream, which is one of the obstacles in creating a blood test. Furthermore, the proteins tau and amyloid are sticky by nature.

Researchers have conducted much research to identify the type of tau in the blood that most likely indicates elevated levels of amyloid and tau in the brain and not anywhere else in the body. Previous studies have examined the ratio of specific types of amyloid beta to other forms, and p-tau217 has surfaced as a tau variant that indicates the formation of amyloid and tau accumulation in the brain [4].

A company, AD-Detect, developed and released a blood test in 2023 to detect amyloid beta proteins. In addition, they designed the ALZpath pTau217 assay, which is exclusive to researchers and enables them to identify this particular kind of tau through a blood test [5].
An international group of scientists from Scandinavia, Europe, and the US were given access to this test free of charge to see how this test compared to employing cerebrospinal fluid to detect Alzheimer’s biomarkers.

Neurological detection of tau and amyloid beta proteins via blood test

In the recent research, researchers examined information from three sources: two biobanks established to study aging and dementia and one cohort of people at risk for Alzheimer’s [1]. The study involved 786 participants—504 female and 282 male—with a mean age of 66. The subjects underwent brain scans and spinal taps, and the researchers collected their blood.

During the data collection process, some subjects displayed indications of cognitive deterioration while others did not. With p-tau217 immunoassay, the researchers were able to identify aberrant beta amyloid and tau in a participant’s blood sample with comparable accuracy and findings compared to the participant’s spinal tap or brain scan.

Data analysis revealed that while the assay could detect people with aberrant levels of tau and amyloid beta, it did not examine a potential correlation between these abnormalities and the occurrence of Alzheimer’s. Researchers evaluated the assay combined with imaging data.

The assay was comparable to cerebrospinal fluid assays in its capacity to identify aberrant levels of tau and amyloid beta, and it offered a more precise diagnosis of hippocampal shrinkage. This was true for each of the three groups.

According to the researchers, 80% of test subjects had aberrant tau and amyloid beta levels that the assay could identify; the other 20% would require cerebrospinal fluid testing or further imaging. They stated that it might help identify patients for early intervention with novel pharmaceutical treatments intended to lower amyloid formation and was more accurate than the diagnostic techniques available today.

The assay creators vetted the publication before its submission to the journal.

The possible limitations

However, while the blood test in this study turned out to be highly accurate in identifying whether someone has significant Alzheimer’s traits in their brain, not everyone who has those characteristics would get the disease.

Additionally, as the p-tau test is only specific for Alzheimer’s, it cannot rule out other probable causes of symptoms such as vascular dementia or Lewy body dementia in patients who test negative but exhibit evidence of cognitive impairment.

In conclusion, a blood test for Alzheimer’s, such as the one illustrated in the new study, can be used to help diagnose both an individual undergoing early memory loss and a patient before they exhibit signs or symptoms of the disease because changes in the brain can occur up to 20 years before overt symptoms appear.


  1. Ashton, N.J., Brum, W.S., Di Molfetta, G., Benedet, A.L., Arslan, B., Jonaitis, E., Langhough, R.E., Cody, K., Wilson, R., Carlsson, C.M. and Vanmechelen, E., 2024. Diagnostic Accuracy of a Plasma Phosphorylated Tau 217 Immunoassay for Alzheimer Disease Pathology. JAMA neurology.
  2. Dementia. World Health Organization. https://www.who.int/news-room/fact-sheets/detail/dementia. Accessed: 12th February, 2024.
  3. Advancing Early Detection. Alzheimer’s Disease and Healthy Aging. Centers of Disease Control and Prevention. https://www.cdc.gov/aging/healthybrain/issue-maps/early-detection.html. Accessed: 12th February, 2024.
  4. Telser, J., Risch, L., Saely, C.H., Grossmann, K. and Werner, P., 2022. P-tau217 in Alzheimer’s disease. Clinica Chimica Acta, 531, pp.100-111.
  5. pTau217: A Transformative Biomarker for Alzheimer’s Disease. ALZpath. https://alzpath.bio/researchers/. Accessed: 12th February, 2024.
  6. Blood test may detect early signs of Alzheimer’s in the brain, study suggests. Medical News Today. https://www.medicalnewstoday.com/articles/alzheimers-blood-test-detect-early-signs-protein-buildup-in-brain. Published Online: 25th January, 2024. Accessed: 12th February, 2024.
  7. New blood test that screens for Alzheimer’s may be a step closer to reality, study suggests. CNN Health. https://edition.cnn.com/2024/01/22/health/alzheimers-blood-test-screening-study/. Published Online: 22nd January, 2024. Accessed: 12th February, 2024.
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