PrecivityAD2 is a blood test that the FDA cleared on August 20, 2026, for adults aged 40 and older who are already showing signs of cognitive impairment. That clearance makes it the first FDA-cleared Alzheimer's blood test available at that younger age, and the third FDA-cleared blood-based biomarker test for the disease overall, according to the Alzheimer's Association. For families watching a younger relative develop new memory problems, the test offers a faster, less invasive way to check for amyloid plaque pathology than a PET scan or spinal tap. It does not stand alone as a diagnosis, and it was not studied in people without symptoms — both limits shape how it should be used in 2026.
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 the August 2026 Clearance Covers
- How Accurate Is the Test?
- Why a Blood Test Changes the Workup
- Getting Access to the Test Now
What PrecivityAD2 Actually Measures
PrecivityAD2 is a blood test made by C2N Diagnostics. It measures two Alzheimer's-related proteins in plasma: the ratio of amyloid beta 42 to 40 (Aβ42/40), and a modified form of tau called %p-tau217.
A mass spectrometry lab combines both readings into a single proprietary measure, the Amyloid Probability Score, which runs from 0 to 100, as described in NeurologyLive's coverage of the clearance. That score sorts a result into one of three categories: negative, positive, or "likely positive." A clinician uses the category, together with the patient's symptoms and other findings, to judge whether amyloid plaques — a hallmark of Alzheimer's disease — are likely present.
Who the August 2026 Clearance Covers
The FDA's clearance applies specifically to adults aged 40 and older who are already undergoing a medical workup for cognitive impairment. C2N's own test catalog is explicit that PrecivityAD2 is not a screening tool: it is meant to be read alongside a clinician's other findings, not used by itself to diagnose Alzheimer's disease, per the C2N/Washington University Neurology Test Catalog. That scope matters for a second reason.
The validation studies behind the test enrolled cognitively impaired research participants, compared against amyloid PET scans as the reference standard. No documentation supports using the test in people who are cognitively unimpaired or symptom-free, so its current clearance does not extend to screening someone who feels fine, according to an independent assessment from Health Technology Wales. Lowering the eligible age to 40 is the clearance's central change. Alzheimer's Association president and CEO Joanne Pike said the expansion "reflects that younger-onset Alzheimer's is a reality for many families" and can help more of them "get clarity and access to care planning sooner," as quoted in the Alzheimer's Association's statement.
How Accurate Is the Test?
Accuracy figures for PrecivityAD2 come from more than one study, and they describe different things, so they are not interchangeable. In the 1,142-person validation behind the August 2026 clearance, C2N reported a 97.6% positive predictive value and a 93.1% negative predictive value for results that fell into the standard positive or negative categories. A separate "likely positive" category, which accounted for 17.3% of participants, carried a lower 77.3% positive predictive value, according to C2N's press release as republished by Cortex STL.
Earlier independent work tells a similar story with different numbers. A validation against amyloid PET in roughly 190 cognitively impaired participants from the ADNI Biorepository found 91% overall accuracy. The original 583-person development study reported 88% accuracy, 88% sensitivity, and 89% specificity at its optimal cutoff, both measured against amyloid PET scans, per the medRxiv preprint. The practical takeaway: a "positive" or "negative" result is highly reliable in these studies, but a "likely positive" result carries more uncertainty and typically calls for additional follow-up rather than treatment decisions based on the blood test alone.
Why a Blood Test Changes the Workup
Before blood-based biomarkers existed, confirming amyloid plaques meant an amyloid PET scan, which costs roughly $6,500, or a lumbar puncture to test cerebrospinal fluid — an invasive procedure many patients want to avoid. PrecivityAD2 replaces that step with a single blood draw, according to C2N's own positioning materials and the Health Technology Wales assessment.
For a younger adult with new memory symptoms, that difference can shorten the path to an answer. A blood draw is easier to schedule, carries no radiation exposure, and can be done in a standard clinic visit rather than requiring referral to a specialized imaging or neurology center for PET or CSF testing.
Getting Access to the Test Now
The FDA-cleared version of PrecivityAD2 is expected to become available later in 2026. In the meantime, C2N continues to offer the test's existing CLIA-validated, laboratory-developed version through its own clinical laboratory, according to LabMedica's coverage. For someone 40 or older experiencing new, persistent memory or thinking problems, a practical first step is a conversation with a physician about an Alzheimer's workup:.
- Ask whether PrecivityAD2 or a comparable biomarker test is available through the clinic or a referral.
- Expect the blood result to be interpreted alongside a cognitive exam and other findings, not treated as a stand-alone diagnosis.
- A "likely positive" result should prompt discussion of further testing, given its lower positive predictive value compared with a standard positive result.
- The test is intended for people already showing cognitive symptoms, not as a general screening tool for someone without symptoms.
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