PrecivityAD2 is a blood test that helps doctors evaluate adults with cognitive symptoms for Alzheimer's disease, and the FDA cleared it for that purpose on August 20, 2026. The clearance makes it the first FDA-cleared Alzheimer's blood test available to adults as young as 40 with cognitive symptoms, lowering the age floor set by earlier blood tests. For someone newly diagnosed with mild cognitive impairment, or a family member trying to understand the diagnostic path, PrecivityAD2 changes what a workup can look like before anyone orders a PET scan or a spinal tap. It does not replace a clinical evaluation, and it is not meant for people without symptoms.
Medical information disclaimer: This article is for general educational purposes only and does not provide medical advice, diagnosis, or treatment. Always consult a physician or other qualified health professional about symptoms, medications, tests, or treatment decisions.
Table of Contents
- What PrecivityAD2 Actually Measures
- Who Is Cleared to Use It, and Who Is Not
- Why This Matters for Mild Cognitive Impairment and Treatment Decisions
- When a Blood Test Can Replace a PET Scan or Spinal Tap, and When It Can't
- Getting Access to the Test Now
What PrecivityAD2 Actually Measures
PrecivityAD2 is made by C2N Diagnostics and runs on a single blood draw. It uses high-resolution mass spectrometry to measure two markers: the amyloid-beta 42/40 ratio and the percentage of phosphorylated-tau217, both tied to the buildup of amyloid plaques in the brain.
The lab combines these into a single number called the Amyloid Probability Score 2, or APS2, which runs from 0 to 100, according to 360Dx. A higher APS2 score indicates a higher probability that amyloid plaques are present, the biological hallmark that distinguishes Alzheimer's disease from other causes of memory or thinking problems. In the FDA validation study of 1,142 participants, a positive result carried a 97.6% positive predictive value and a negative result carried a 93.1% negative predictive value for brain amyloid, each benchmarked against amyloid PET or spinal fluid testing, as reported by Newswise.
Who Is Cleared to Use It, and Who Is Not
The FDA's cleared indication covers adults age 40 and older who already have signs or symptoms of cognitive impairment and are being evaluated for Alzheimer's disease or another cause of cognitive decline. Practical Neurology reports that the test is explicitly not intended as a screening tool for people without symptoms, and it is not meant to stand alone as a diagnosis. That distinction matters for anyone considering the test. A person with no memory complaints cannot use PrecivityAD2 as a general risk check, and a positive result on its own does not constitute an Alzheimer's diagnosis.
It is designed to be one input a clinician weighs alongside a cognitive exam, medical history, and other testing, as part of a broader workup for someone already showing symptoms. The clearance also widens who can be tested by age. Fujirebio's Lumipulse test, cleared in 2025, was limited to adults 55 and older. PrecivityAD2 drops that floor to 40, making it the third FDA-cleared Alzheimer's blood test overall, according to the Alzheimer's Drug Discovery Foundation.
Why This Matters for Mild Cognitive Impairment and Treatment Decisions
Mild cognitive impairment, often shortened to MCI, describes a noticeable decline in memory or thinking that is not yet severe enough to interfere with daily independence. It sits between normal aging and dementia, and it is the stage where confirming or ruling out amyloid pathology carries the most weight, because treatments like lecanemab (sold as Leqembi) are only approved for MCI and mild dementia tied to confirmed amyloid buildup. A published retrospective study of 143 patients with cognitive concerns found that among 34 who went on to receive lecanemab, the median APS2 score was 97.
Among the subset who also had confirmatory CSF or PET testing, every patient who tested positive on the blood test was confirmed positive on the gold-standard test, according to the peer-reviewed study on PMC. That pattern supports using the APS2 score to help establish the amyloid pathology that Leqembi's label requires before treatment begins. For a patient and family weighing a treatment like Leqembi, this means a blood draw can now do work that used to require a PET scan or lumbar puncture to get a treatment conversation started, even though confirmatory testing may still follow depending on the result and the clinical picture.
When a Blood Test Can Replace a PET Scan or Spinal Tap, and When It Can't
The Alzheimer's Association's first clinical practice guideline on blood-based biomarkers, released at its 2025 conference, sets the bar for how a blood test like PrecivityAD2 can be used. A test with at least 90% sensitivity and at least 75% specificity qualifies as a triage tool, useful for deciding who needs further workup.
A test reaching at least 90% sensitivity and at least 90% specificity clears a higher bar: it can substitute for confirmatory PET or CSF testing in specialty care, according to the Alzheimer's Association guideline. The guideline is explicit that not all blood biomarker tests are equivalent, so a clinician evaluating a patient with MCI needs to confirm which tier a given PrecivityAD2 result falls into before treating it as a substitute for PET or CSF confirmation, rather than a triage step, as summarized by Patient Care Online. In practice, this means a patient should ask their neurologist or memory specialist directly whether the result is being used to decide on further testing or to make a final treatment decision.
Getting Access to the Test Now
C2N Diagnostics has stated that the FDA-cleared version of PrecivityAD2 is expected to become available later in 2026. In the meantime, the existing CLIA-validated version of the test, run as a laboratory-developed test through C2N's own clinical laboratory, remains available now, according to a C2N statement reported by CLP Magazine. A patient or caregiver interested in testing should expect these practical steps:.
- Confirm with a primary care physician, neurologist, or memory clinic that cognitive symptoms are present and documented, since the test is cleared only for people already showing signs of decline.
- Ask whether the clinic orders through C2N's current CLIA-validated lab process or plans to wait for the FDA-cleared version later in 2026.
- Ask how the result will be used: as a triage step toward PET or CSF testing, or as a basis for a treatment decision such as starting lecanemab.
- Expect a single blood draw, with results reported as an APS2 score rather than a simple positive or negative label.
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