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A newly cleared blood test could make it easier for doctors to evaluate patients showing possible signs of Alzheimer’s disease, potentially shortening a diagnostic process that has traditionally relied on brain scans and spinal taps.

The Food and Drug Administration (FDA) has cleared PrecivityAD2 for use in adults aged 40 and older who have signs or symptoms of cognitive decline. The test, developed by C2N Diagnostics, uses a single blood sample to look for biomarkers associated with amyloid plaques in the brain — a defining feature of Alzheimer’s disease.

The underlying technology was developed by researchers at Washington University School of Medicine in St. Louis, whose work led to the creation of C2N Diagnostics.

“The PrecivityAD2 test provides an accurate and reliable way to detect the presence of brain amyloid plaques associated with Alzheimer’s disease pathology based on a single blood draw,” Dr. Randall Bateman, a Washington University neurologist and C2N co-founder, said in the university’s announcement.

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How the test works

PrecivityAD2 uses high-resolution mass spectrometry to measure specific forms of amyloid and tau proteins in the blood. Those measurements are combined to produce a score estimating the likelihood that a patient has amyloid plaques.

In a clinical validation study involving 1,142 people with signs or symptoms of cognitive decline, a positive result had a 97.6% positive predictive value, meaning nearly 98% of those receiving that result had amyloid pathology confirmed through a brain scan or cerebrospinal fluid test. A negative result had a 93.1% negative predictive value.

Earlier studies found that the test could identify Alzheimer’s-related amyloid pathology with more than 90% accuracy, including among patients with mild cognitive symptoms.

The blood test may offer a simpler alternative to positron emission tomography (PET) brain scans and cerebrospinal fluid testing, which require a lumbar puncture, commonly called a spinal tap. Those procedures can be expensive, time-consuming, or difficult to access.

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Not a standalone diagnosis

Consumers should understand that the test does not diagnose Alzheimer’s disease by itself. It is intended to aid a broader clinical evaluation performed by a healthcare professional experienced in assessing cognitive problems.

The test is also not cleared for screening people who have no symptoms. Memory problems can have many causes, including medication side effects, depression, sleep disorders, vitamin deficiencies, and other forms of dementia.

Some patients may also receive an intermediate or “likely positive” result requiring additional evaluation. Doctors may still recommend a PET scan, spinal-fluid analysis, or other testing before making a diagnosis or prescribing treatment.

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Why earlier detection matters

An earlier, more accurate evaluation has become increasingly important with the arrival of drugs that can slow the progression of Alzheimer’s in some patients. These treatments generally work best when given during the disease’s early stages, but they carry risks and require confirmation that amyloid is present.

A blood test could also make Alzheimer’s evaluations more accessible in communities without specialized imaging equipment or memory clinics.

FDA clearance means the agency determined that PrecivityAD2 was substantially equivalent to an existing legally marketed device. That is different from the FDA approval process used for many new drugs and certain high-risk medical devices.

The FDA-cleared version of PrecivityAD2 is expected to become available later in 2026. A laboratory-developed version is already available through C2N’s clinical laboratory and must be ordered by a licensed healthcare provider. Insurance coverage and patients’ out-of-pocket costs may vary.