The FDA cleared PrecivityAD2, a blood test for Alzheimer's-related brain changes, on Aug. 20, 2026, C2N Diagnostics announced in the company announcement. It is for adults 40 and older with signs of cognitive impairment who are being evaluated for Alzheimer's, the Alzheimer's Association reports in its clearance summary.
The test needs only a single blood draw. Open Access Government described it as over 90% accurate and comparable to PET scans and spinal taps in its August 2026 report. It offers a less invasive way to rule Alzheimer's in or out earlier, according to that report.
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 C2N — Use this primary source to verify the official guidance.
- Read the official guidance from Alz — Use this primary source to verify the official guidance.
Table of Contents
- Why does starting at age 40 matter?
- What does the blood sample measure?
- How accurate is the result?
- What are the limits?
- What should you do about new symptoms?
Why does starting at age 40 matter?
PrecivityAD2 is the first FDA-cleared Alzheimer's blood test indicated from age 40, FixFirst Research notes. Fujirebio Lumipulse, cleared in May 2025, and Roche Elecsys pTau181, cleared in October 2025, both start at age 55. That ten-plus year gap matters for younger adults seeking answers.
Most memory clinics see few patients under 55, but early-onset symptoms do occur. A cleared blood option from age 40 gives doctors in that age group a defined path to check amyloid buildup. It does not expand testing to people without symptoms.
What does the blood sample measure?
C2N Diagnostics says the test uses high-resolution mass spectrometry, a precise lab method that identifies proteins by weight. It measures the amyloid-beta 42/40 ratio, meaning the balance of two amyloid fragments, plus p-tau217 relative to non-phosphorylated tau217, meaning a modified Alzheimer's-linked tau form versus its normal form.
Those results feed an Amyloid Probability Score 2, a calculated score that estimates the likelihood of amyloid buildup in the brain. The score is not a memory grade and not a final diagnosis. A clinician reads it with exams, history, and other findings.
How accurate is the result?
In a 1,142-person validation study, a positive result predicted amyloid buildup 97.6% of the time and a negative result ruled it out 93.1% of the time, FixFirst Research reports in FixFirst Research analysis. That performance puts a blood draw close to far more demanding procedures.
No test is perfect, so a small share of results will mislead. An experienced clinician decides whether imaging, spinal fluid testing, or repeat assessment is still needed.
- A positive result means amyloid buildup is highly likely and needs clinical follow-up.
- A negative result means amyloid buildup is unlikely, which points evaluation elsewhere.
What are the limits?
The test aids diagnosis with clinical assessment by experienced professionals, the Alzheimer's Association states. It is not a standalone diagnosis and not screening for adults without symptoms. A result alone cannot label someone as having Alzheimer's.
That limit shapes where testing happens. Ordering and interpretation belong in a clinic that evaluates cognition, not in a health fair or home kit. People without new impairment do not meet the cleared use.
What should you do about new symptoms?
Start with a clinical visit, not a test request. Describe what changed, when it started, and how it affects work, bills, driving, or household tasks.
Bring concrete examples rather than general worry. Bring those notes, medication bottles, and your observer to the appointment.
- Track two to three recent lapses with dates.
- List medications, sleep problems, and mood changes.
- Bring someone who has noticed the changes.
- Ask what evaluation is planned and whether an Alzheimer's blood test fits.
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