There is an update in the world of Alzheimer’s disease blood tests. This January, the Taiwan Food and Drug Administration approved three immunoassays developed by the biotech company MagQu Co., based in New Taipei City, that measure Aβ40, Aβ42, and total tau in plasma. These products can be used to aid doctors or medical technologists in their diagnosis of Alzheimer’s disease and amnestic mild cognitive impairment, or they can be used to evaluate risk for dementia, Shieh-Yueh Yang, the president of MagQu, wrote to Alzforum. The agency’s approval categorizes the test as supportive, however; PET scans or clinical tests will still be required for a formal diagnosis.

  • MagQu plasma Aβ and tau assay identify individuals with AD or amnestic MCI.
  • Assays match with clinical diagnoses 80 percent of the time.
  • This product offers another tool to help doctors diagnose AD and aMCI.

In 2018, researchers from Taipei Medical University, Taiwan, found that 5.63 per 1,000 people aged 75 to 84 years old were diagnosed with AD, and that number escalated to 8.17 per 1,000 people in 2010 (Hung et al., 2016). 

Colin Masters of the University of Melbourne, Australia, sees this as an exciting time for plasma Aβ and tau assays. “MagQu technology is very interesting and differs considerably from all the others. Their assay shows an Aβ42 signal that increases with AD, whereas all the other assays are driven by a drop in this signal,” wrote Masters, who is on the Scientific Advisory Committee for MagQu (Teunissen et al., 2018Lue et al., 2017). 

When MagQu presented its findings at the 2018 Alzheimer’s Association International Conference in London, scientists were puzzled by this Aβ42 increase (Aug 2018 conference news). To capture and quantify each protein, the MagQu assays use a single antibody conjugated to magnetic nanobeads, followed by a magnetic spin technology that detects antigen-antibody complexes (Yang et al., 2017). In a process called immunomagnetic reduction, the rotation of the particles in a magnetic field slows once they bind their target, and this deceleration can be detected by a powerful magnetic sensor called a superconducting quantum interference device (Apr 2018 conference news). This contrasts other assays for plasma Aβ and tau, which either use two antibodies, one for capture and one for detection, or one antibody for capture along with mass spectrometry for detection. This is generally thought to increase specificity.

Using cut-off values of combined plasma biomarkers, including Aβ42/tau and Aβ42/Aβ40, MagQu reported that they could differentiate individuals with aMCI and AD from healthy controls about 80 percent of the time. “Once the levels of combined plasma biomarkers are higher than the cutoff values, the subject would be strongly advised to get further tests, such as amyloid PET, MRI, and neuropsychological tests,” wrote Yang.

Last November, MagQu reported a similar assay for plasma TDP-43, a promising biomarker for frontotemporal dementia, amyotrophic lateral sclerosis, and other neurodegenerative diseases (Yang et al., 2020). 

MagQu isn’t the only corporation working on Alzheimer’s blood tests. In 2018, Masters and colleagues from Shimadzu Corp. unveiled a mass spectrometry-based test for blood Aβ  that predicted brain amyloid status with up to 90 percent accuracy (Feb 2018 news). Masters and Akinori Nakamura from the National Center for Geriatrics and Gerontology in Aichi, Japan, are analyzing a large set of data on this blood assay in a validation study. Other companies, including Quanterix, Roche Diagnostics, and Fujirebio have assays in development. C2N Diagnostics recently gained CLIA approval for its Precivity mass-spec test for Aβ (Nov 2020 news). 

“The market for a high-performance AD blood test is so large that I think many players will emerge,” wrote Masters.—Helen Santoro

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References

News Citations

  1. With Sudden Progress, Blood Aβ Rivals PET at Detecting Amyloid
  2. After Plasma Aβ, Now Plasma P-Tau181 Shows Promise
  3. Closing in on a Blood Test for Alzheimer’s?
  4. Plasma Aβ Test Wins Approval—Are p-Tau Tests Far Behind?

Alzpedia Citations

  1. TDP-43

Paper Citations

  1. . The epidemiology and burden of Alzheimer's disease in Taiwan utilizing data from the National Health Insurance Research Database. Clinicoecon Outcomes Res. 2016;8:387-95. Epub 2016 Aug 2 PubMed.
  2. . Plasma Amyloid-β (Aβ42) Correlates with Cerebrospinal Fluid Aβ42 in Alzheimer's Disease. J Alzheimers Dis. 2018;62(4):1857-1863. PubMed.
  3. . Plasma Levels of Aβ42 and Tau Identified Probable Alzheimer's Dementia: Findings in Two Cohorts. Front Aging Neurosci. 2017;9:226. Epub 2017 Jul 24 PubMed.
  4. . Detection of Plasma Biomarkers Using Immunomagnetic Reduction: A Promising Method for the Early Diagnosis of Alzheimer's Disease. Neurol Ther. 2017 Jul;6(Suppl 1):37-56. Epub 2017 Jul 21 PubMed.
  5. . Development of Assaying Plasma TDP-43 Utilizing Immunomagnetic Reduction. Journal of Neurological Disorders. November 4, 2020.

Further Reading

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