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Skin Test Accurately Identifies Alzheimer’s Disease

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A new study suggests that a minimally invasive skin test can accurately diagnose Alzheimer’s disease (AD) with high sensitivity and specificity even in the presence of comorbidities.

Dr. Daniel Alcon

The test, which measures factors related to synaptic connections in the brain, can be added to other tests to “extremely increase confidence in decision making.” [an AD] diagnosis,” Daniel Alcon, MD, chief scientific advisor for SYNAPS Dx, the company that developed the test, told Medscape Medical News.

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The results were presented at the Alzheimer’s Association International Conference (AAIC) 2022.

Better specificity required

Clinical trials of potential treatments for AD typically include patients without a definitive diagnosis of AD dementia. This is because diagnoses are often uncertain, especially during the first 4-5 years of illness.

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Several tests have been developed to detect signs of AD. These include MRI and PET scans to detect amyloid plaques, cerebrospinal fluid, and measure soluble plasma amyloid and tau, as well as blood tau levels.

However, none of these tests were thoroughly confirmed at autopsy, Alcon said. Previous studies have shown that more than 50% of patients do not have only AD. Instead, they also have other pathologies, such as Parkinson’s disease, frontal lobe dementia, or dementia with multiple infarcts, Alcon noted.

“It’s not enough for a test to distinguish Alzheimer’s disease from a non-demented control person. It is only valuable if you can distinguish it from other types of dementia,” Alcon said.

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He noted that while amyloid beta and tau are used as “pathological red flags” for detecting Alzheimer’s disease at autopsy, they are not good for definitive diagnosis of the disease because they are not closely associated with cognitive deficits.

There is an “urgent unmet medical need” for a highly accurate and readily available Alzheimer’s biomarker, he said.

Use the industry-certified DISCERN test (SYNAPS Dx), which measures factors associated with synaptic connections in the brain, which Alcon says is a better indicator of Alzheimer’s than amyloid or tau. Such factors include synapse loss, neuronal death, inflammation, amyloid deposition, and tau hyperphosphorylation.

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One of the analyzes in the test is the morphometric imaging analysis, which has previously shown a strong correlation of skin cell abnormalities with dementia and the presence of AD pathology in the brains of AD patients.

“Studies correlate what’s going on in a patient’s brain with what’s going on elsewhere,” Alcon said. [that] the disease has a systemic expression; it affects not only the brain, but the entire system.”

New and unique?

In the current study, researchers obtained a small skin sample through skin biopsy from 74 participants. Of these participants, 26 had Alzheimer’s disease, which was later confirmed after autopsy; 21 had dementia without AD (non-ADD); and 27 did not have dementia and served as controls.

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The researchers found that the AD cell lines formed large aggregates, while the cell samples without ADD or the control group formed smaller and more numerous aggregates. The researchers then counted the number of aggregates and measured their average area.

This allowed them to distinguish patients with AD from those without ADD. The probability distributions of morphometric imaging signals showed a clear separation of measures for individual patients with AD and group values ​​for patients without ADD.

Based on these results, the sensitivity of the MI test for diagnosing AD was defined as 100% (95% CI, 86% – 100%), and the specificity was also 100% (95% CI, 84% – 100%). .

The researchers also used samples from patients with dementia older than 55 who underwent blind autopsy. The specificity of AD was maintained even in cases of comorbidities, including AD with dementias such as Parkinson’s disease, Pick’s disease, and frontal dementia.

“What’s new and unique is that we’ve shown that we can measure Alzheimer’s disease even in patients with comorbidities, that is, patients with other dementias,” Alcon said.

Next steps

Alcon noted that this type of research is time-consuming and requires “resources, perseverance and determination.” Death and confirmatory autopsy may occur years after skin testing and clinical diagnosis.

The company’s core lab is already analyzing samples with suspected Alzheimer’s disease, but “we are preparing to launch nationally,” Alcon said.

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“Before making a diagnosis of Alzheimer’s disease, clinicians must use all the measurements at their disposal, and they must be thorough and careful,” he added.

The company is currently seeking approval for the skin test by the US Food and Drug Administration and has received breakthrough status.

Alcon said the test could help rule out other causes of dementia for which there are treatments, such as a thyroid disorder, major depression and vitamin B12 deficiency.

He acknowledged that if the test does indicate Alzheimer’s disease, there are few effective treatments. “In my opinion, none of the drugs available today actually treat the underlying disease,” he said.

However, he noted that it could change. Alcon is also president of Synaptogenix, a company developing a therapeutic agent that aims to enhance the synaptic growth pathway.

First days

Commenting on the study for Medscape Medical News, Rebecca Edelmeier, Ph.D., senior director of research at the Alzheimer’s Association, said she is encouraged by this skin prick test and other research in diagnosing Alzheimer’s disease.

However, she warned that these tests are at a very early stage. “An important step in advancing these tests for wider use is to study them in large-scale clinical trials,” said Edelmeier.

She noted that the DISCERN test analyzes protein kinase C (PKC) signaling markers, which have not yet been validated in large studies, to support their use as a diagnosis of AD.

Edelmeier also indicated that this test does not have FDA clearance. “It’s important for consumers to be informed about how widely these tools have been evaluated,” she said.

She added that currently there is no single test that would diagnose Alzheimer’s disease.

The study was funded by SYNAPS.

Alzheimer’s Association International Conference (AAIC) 2022: abstract 63141. Submitted July 31, 2022.

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