Blood test for Alzheimer’s shows 100 percent accuracy in early trials

A reliable blood test for Alzheimer’s may one day become a vital tool for early diagnosis(Credit: National Eye Institute/Creative Commons)

Alzheimer's can be quite a stealthy foe, at times causing damage in a sufferer long before any symptoms start to show. Naturally, this makes it tricky to detect early on, which is problematic because treatment options only narrow as the disease progresses. But researchers may have now uncovered what could become a hugely valuable diagnostics tool, developing a blood test capable of picking up early stage Alzheimer's with "unparalleled accuracy."

"It is now generally believed that Alzheimer's-related changes begin in the brain at least a decade before the emergence of telltale symptoms," says Dr. Robert Nagele, from Rowan University School of Osteopathic Medicine. "To the best of our knowledge, this is the first blood test using autoantibody biomarkers that can accurately detect Alzheimer's at an early point in the course of the disease when treatments are more likely to be beneficial – that is, before too much brain devastation has occurred."

Studies have shown how the disease wreaks havoc in its formative stages, destroying brain cell connections that later leads to common symptoms like memory loss and confusion. Researchers are working toward methods that would enable earlier detection of the disease, with non-invasive MRIs and biosensors approaches that have shown real potential in recent times.

And blood tests are a particularly promising avenue to early diagnosis. In 2014, a team of international scientists identified a set of biomarkers that could predict with 87 percent accuracy whether a person with Mild Cognitive Impairment (MCI) would progress to Alzheimer's disease within a year. While MCI can be a sign of early Alzheimer's, it can also arise from a number of other health conditions, so an ability to tell the difference could mean big things when it comes to managing the disease.

"About 60 percent of all MCI patients have MCI caused by an early stage of Alzheimer's disease. The remaining 40 percent of cases are caused by other factors, including vascular issues, drug side-effects and depression," says Cassandra DeMarshall, PhD candidate at Rowan University. "To provide proper care, physicians need to know which cases of MCI are due to early Alzheimer's and which are not."

Led by Nagele, the Rowan University team took blood samples from 236 patients, 50 of which had been diagnosed with Alzheimer's due to the low-level presence of amyloid-beta 42 peptide in their cerebrospinal fluid. These are the peptides that gather in clusters and go on to form amyloid plaques in the brain, which are considered the culprits behind the debilitating disease.

Also among the participants was a control group of 50, along with 50 subjects with MCI, 50 with Parkinson's, 25 with multiple sclerosis and 11 with breast cancer. The blood samples were screened with human protein microarrays, each with 9,486 unique proteins, as a way of drawing out autoantibodies that were indicative of the different diseases.

The researchers identified the top 50 autoantibody biomarkers that were capable of detecting early-stage Alzheimer's. Across a number of tests, this set of biomarkers could distinguish between MCI sufferers with and without Alzheimer's with 100 percent precision. The test could also tell the difference between the early Alzheimer's and more advanced with 98.7 percent accuracy, early Parkinson's (98 percent) and both multiple sclerosis and breast cancer (100 percent).

"Our results show that it is possible to use a small number of blood-borne autoantibodies to accurately diagnose early-stage Alzheimer's," says DeMarshall. "These findings could eventually lead to the development of a simple, inexpensive and relatively noninvasive way to diagnose this devastating disease in its earliest stages."

The researchers are now setting their sights on reproducing these promising results in a larger study. And if they are successful, it raises the possibility of a reliable way to pick up the disease early on, which could help preserve the quality of life for sufferers through less drastic treatment regimes.

The research was published in the journal Alzheimer's & Dementia: Diagnosis, Assessment & Disease Monitoring.

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