Alzheimer’s Diagnostic Blood Test Offers Accurate Alternative to PET Scans and Cerebrospinal Fluid Tests
Posted on 22 Aug 2023
Alzheimer's disease stands as the leading cause of dementia in older adults, progressively eroding memory and cognitive abilities. In the years before the early 2000s, definitive confirmation of Alzheimer's disease in an individual only came posthumously through autopsy. However, the diagnostics landscape has transformed with the strides made in research; today, laboratory and imaging tests have emerged to unveil the biological indicators of the disease, referred to as biomarkers, while the person is still alive. Taking a stride forward, a blood test aims to establish a new benchmark for blood-based biomarkers in diagnosing Alzheimer's through a combined assessment of amyloid beta (Aβ42/40) and tau protein (p-tau217/np-tau217) ratios.
C₂N Diagnostics (St Louis, MO, USA) has introduced the PrecivityAD2 blood test—a clinical care assay that meets the existing standard of care comprising PET scans and cerebrospinal fluid tests. Tailored to alleviate the bottlenecks and unmet needs of healthcare providers and patients alike, the PrecivityAD2 test aids the assessment of individuals displaying symptoms of Alzheimer's disease or other forms of cognitive decline. This analytically and clinically validated blood test empowers healthcare practitioners to either confirm or rule out Alzheimer's in patients exhibiting mild cognitive impairment or dementia. The test employs a dual measurement of specific plasma amyloid beta and tau peptide concentrations, resulting in the determination of the Aβ42/40 Ratio and p-tau217/np-tau217 (p-tau217 Ratio).
What sets this test apart is the integration of plasma analyte ratios facilitated by the company's proprietary mass spectrometry techniques. This inclusion makes the test more robust and negates the influence of confounding factors such as chronic kidney disease and cardiovascular ailments. The calculated ratios are combined into a specialized statistical algorithm, leading to the derivation of the Amyloid Probability Score 2 (APS2). This numerical score, ranging from 0 to 100, functions as a determinant of a patient's likelihood—either Positive (indicating high probability) or Negative (indicating low probability)—of harboring brain amyloid plaques as observed in amyloid PET scans. When validated through clinical investigations encompassing two separate cohorts totaling 583 individuals with cognitive impairments, and using amyloid PET scans as the gold standard, the PrecivityAD2 blood test demonstrated an impressive overall test performance statistic of 0.94 AUC (Area Under the Curve) and 88% accuracy.
“We believe the PrecivityAD2 test represents the next generation in blood biomarker tests and will help establish a new standard in Alzheimer’s disease diagnosis. The 2022 Clinical Trials on Alzheimer’s Disease Task Force report outlined that combined biomarkers can be especially helpful in avoiding misdiagnosis, and PrecivityAD2 does just that by harnessing two established biomarkers in one assay. We believe the test addresses a major unmet need for an accurate, safe, non-invasive, and accessible alternative to amyloid PET scans and lumbar punctures,” said Dr. Joel Braunstein, C2N’s president and CEO. “This announcement is timely with the approval of new disease modifying therapies and others on the way along with the ability for healthcare providers to more easily refer patients to sites or to mobile phlebotomists where their blood can be drawn for diagnosis.”
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