Scientists develop a blood test that can spot Alzheimer's disease early

Alzheimer's disease is an irreversible neurodegenerative disease, and there is still no way to treat it. Many cases of the condition are diagnosed when the disease has already progressed, making it difficult to manage. Now, researchers have developed a new test that can spot Alzheimer's disease early on.

The study findings, which were announced at the Alzheimer's Association International Conference, showed that the new Alzheimer's disease test had extremely high accuracy for detecting chemicals in the blood that are specific for the illness.

Image Credit: Lightspring / Shutterstock
Image Credit: Lightspring / Shutterstock

What is Alzheimer's disease (AD)?

Alzheimer's disease is a form of dementia that affects memory, thinking, and behavior. The common symptoms of the illness worsen overtime enough to interfere with daily tasks.

About 5.8 million people over 65 years old in the United States live with Alzheimer's disease, but the number could triple by 2050. It is considered the 6th leading cause of death among Americans. Across the globe, dementia is estimated to affect 60 million people.

At present, Alzheimer's disease is diagnosed using a combination of memory tests and brain scans, only when symptoms start to appear. When these symptoms appear, the condition has already progressed, affecting a person's memory, cognitive skills, and behavior.

Blood test

The idea of a blood test for dementia is not new, but the two latest studies indicate that the presence of the protein tied to Alzheimer's disease in the blood could be used to detect those who may develop the illness at a much earlier age.

The first study, published in JAMA, aimed to examine plasma tau phosphorylated at threonine 217 (P-tau217) as a biomarker for AD.

The research team has reported the results of multiple studies on advances in blood tests that can detect abnormal versions of the tau protein, which can detect changes in the brain about 20 years before dementia symptoms appear. A specific form of tau, called p-tau217, seems to be the most specific one to Alzheimer's disease and the earliest to show measurable changes.

The team, composed of international scientists, has reported that the blood test that measures the protein tau accurately distinguished Alzheimer's disease from other forms of dementia in 89 to 98 percent of the cases.

"Among 1,402 participants from 3 selected cohorts, plasma P-tau217 discriminated AD from other neurodegenerative diseases, with significantly higher accuracy than established plasma- and MRI-based biomarkers and its performance were not significantly different from key CSF- or PET-based measures," the researchers wrote in the paper.

"Further research is needed to optimize the assay, validate the findings in unselected and diverse populations, and determine its potential role in clinical care," they added.

Further explanation shows that p-tau217 was elevated about seven-fold in Alzheimer's and in people who have a gene that causes the condition. The team added that these levels begin to increase even two decades before the onset of cognitive impairment.

If the test is confirmed and verified, it could open the possibility of early diagnosis of Alzheimer's disease. Doctors can help slow the progression of the disease or even stop it, providing a chance for those with the AD gene to have a good quality of life when they reach 65 years old and above.

Comparing two biomarkers

Other studies have also shown that p-tau181 is more than three times as high in people with AD compared to healthy older adults or those with a condition called frontotemporal lobar degeneration (FTLD).

Another team of researchers, headed by Elisabeth Thijssen and Dr. Adam Boxer of the University of California San Francisco (UCSF) Memory and Aging Center, has reported a comparison of both the tau proteins 181 and 217 to see which can provide the best accuracy in detecting people with Alzheimer's disease.

The study involved 617 participants, including 119 health controls, 74 people with AD, and 294 with FTLD. When the team compared the two biomarkers, they found that P-tau181 had a 91 percent accuracy, while P-tau217 had a 96 percent accuracy in predicting whether a person had a tau positive brain scan.

The study shows that both the biomarkers can detect if a person could develop AD in the future, which can be alternatives to PET scans, which are expensive. Further research and testing are still needed to determine if these tests could help diagnose Alzheimer's disease.

Journal references:
  • Palmgvist, S., Janelidze, S., Quiroz, Y., Zetterberg, H. et al. (2020). Discriminative Accuracy of Plasma Phospho-tau217 for Alzheimer Disease vs Other Neurodegenerative Disorders.  JAMA.
  • Shorena Janelidze, PhD, et al. Plasma phospho-tau217 is a potential early diagnostic and prognostic biomarker of Alzheimer's disease. (Funder(s): Swedish Research Council, the Knut and Alice Wallenberg Foundation, and the Swedish Alzheimer Foundation)
Angela Betsaida B. Laguipo

Written by

Angela Betsaida B. Laguipo

Angela is a nurse by profession and a writer by heart. She graduated with honors (Cum Laude) for her Bachelor of Nursing degree at the University of Baguio, Philippines. She is currently completing her Master's Degree where she specialized in Maternal and Child Nursing and worked as a clinical instructor and educator in the School of Nursing at the University of Baguio.


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