Adults showing cognitive impairment can now access a blood test cleared by the FDA to detect sticky brain plaques tied to Alzheimer’s disease, lowering the barrier to early detection that previously relied on costly spinal taps or PET scans.
A blood test called PrecivityAD2 was cleared by the U.S. Food and Drug Administration on August 20, 2026, marking a shift in how doctors evaluate early memory concerns. The diagnostic tool measures two protein ratios in a single blood draw: one comparing two forms of amyloid protein, and another tracking p-tau217, a tau protein variant linked to brain damage.
These ratios feed into a numerical score ranging from 0 to 100 that reflects the likelihood of amyloid pathology. When tested during FDA evaluation, the assay correctly ruled in amyloid plaques about 98 percent of the time.
Primary Care Doctors Order Blood Diagnostics for Referrals
The arrival of accessible blood diagnostics coincides with broader changes in clinical practice. Primary care doctors and geriatricians can now order these tests directly, allowing specialists like USC neurologist Dr. Helena Chui to receive patient referrals who arrive with their blood work already completed. Before blood tests arrived a couple of years ago, a primary care doctor could often tell a family only that a parent had mild cognitive impairment or dementia without confirming an underlying cause.
To support this decentralized testing model, researchers have also examined how well blood biomarkers withstand everyday clinical handling. A prospective observational study published in Alzheimer’s Research & Therapy evaluated the Elecsys Phospho-Tau (181P) plasma immunoassay developed by Roche Diagnostics. Investigators at LMU Hospital determined how the pTau181 biomarker withstands pre-analytical handling in an intended-use population.
Detecting Synaptic Changes in Down Syndrome
Blood biomarkers are also being explored in high-risk populations. Researchers evaluated serum beta-synuclein as an indicator of early synaptic changes associated with Alzheimer’s disease at the Sant Pau Research Institute in Barcelona. The work analyzed participants, including those with Down syndrome.
Because symptomatic Alzheimer’s affects 90% to 100% of individuals with Down syndrome by their seventh decade, tracking biomarker trajectories provides a window into preclinical disease. Beta-synuclein levels were 1.83 times higher in asymptomatic people with Down syndrome than in controls, 2.82 times higher in the prodromal stage and 3.67 times higher in people with dementia.
Visual Processing Tests for Lewy Body Disease
While blood assays target molecular pathology, complementary diagnostic techniques are emerging for related neurodegenerative conditions. University of Queensland researchers have developed specialized visual tests to detect early signs of Lewy body disease, which includes Parkinson’s disease and dementia with Lewy bodies. Led by neurologist Professor Peter Nestor and study lead author Dr. Emily McCann, the research team assessed 53 people with Lewy body disease and 29 with Alzheimer’s disease.
The assessment evaluates the brain’s visual pathways, including the dorsal stream, tested by identifying numbers formed from the absence of background noise in a field of black dots. The findings revealed that visual problems were worse for those with Lewy body disease than Alzheimer’s disease, offering clinicians a tool to detect the very earliest signs of emerging dementia.