On August 20, 2026, the FDA cleared PrecivityAD2, a C2N Diagnostics blood test that helps detect Alzheimer's-related brain amyloid buildup in patients being evaluated for the disease. Amyloid buildup means sticky protein deposits in the brain linked to Alzheimer's.
NeurologyLive reported the clearance date and use in its FDA clearance report. The clearance covers symptomatic adults age 40 and older. That means the test is for people with memory or thinking symptoms, not for routine screening.
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.
Official resources:
- Read the official guidance from Neurologylive — Use this primary source to verify the official guidance.
- Read the original report from Practicalneurology — Use this primary source to review the complete report.
Table of Contents
- Who can ask about it?
- What does one blood draw measure?
- How accurate is it for clinic patients?
- What does likely positive mean?
- How should you use it at your visit?
Who can ask about it?
The test is cleared for adults 40 and older who have cognitive symptoms and are being evaluated for Alzheimer's disease. NeurologyLive noted it is the first FDA-cleared Alzheimer's blood test for patients that young, below the age 55 floor of earlier cleared tests.
You may fit this group if you have ongoing memory concerns that affect daily life. Your clinician will still review history, exams, and other causes first.
- age 40 or older with memory or thinking symptoms
- evaluation for possible Alzheimer's disease
- care led by a clinician experienced in cognitive disorders
- no use as population screening or stand-alone diagnosis
What does one blood draw measure?
The single-draw test uses high-resolution mass spectrometry to measure two blood ratios: Aβ42/40 and p-tau217/np-tau217. Those ratios reflect amyloid-related changes in the blood. Practical Neurology described the method and score in its test summary.
The lab combines both ratios into an Amyloid Probability Score 2. The report reads negative, likely positive, or positive. Negative points away from brain amyloid. Positive points toward it.
How accurate is it for clinic patients?
In a 1,142-person study of people with cognitive symptoms, results were checked against amyloid PET scans or spinal-fluid biomarkers. A positive result was correct 97.6% of the time. A negative result was correct 93.1% of the time.
Accuracy stayed steady across age groups and 12 other conditions. Those included chronic kidney disease, atrial fibrillation, and diabetes. That steadiness matters because those conditions often distort blood amyloid measures in memory clinics.
What does likely positive mean?
About 17.3% of study participants had an intermediate likely-positive result. In that group, a positive signal was correct only 77.3% of the time. Those patients still need more workup.
That workup may mean a PET scan, spinal-fluid test, or closer follow-up. Your clinic can explain which next step fits your health and preferences. Do not treat likely positive as a final answer.
How should you use it at your visit?
FDA labeling limits the test to use alongside clinical evaluation by clinicians experienced in cognitive disorders. AJMC, reporting an Alzheimer's Association statement, described that limit in its clearance coverage. Ask what your result would change.
It may guide referral, further testing, or treatment planning. For clinic planning, C2N still offers PrecivityAD2 as a CLIA lab test while the FDA-cleared kit was expected to reach U.S. clinicians later in 2026.
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