On Aug. 20, 2026, the Food and Drug Administration cleared PrecivityAD2 to help diagnose Alzheimer's disease alongside standard clinical workup.
PrecivityAD2 is a blood test from C2N Diagnostics that looks for amyloid pathology tied to Alzheimer's, according to the company in its C2N Diagnostics clearance announcement. This briefing explains who qualifies, what the test measures, and how a memory clinic can use the result. It is written for patients who already notice memory or thinking changes.
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 Biospace — Use this primary source to verify the official guidance.
Table of Contents
- Who is cleared to discuss it with a doctor?
- What does the blood sample measure?
- How well did it match PET or spinal fluid?
- How will memory clinics use it?
Who is cleared to discuss it with a doctor?
The test is cleared for adults age 40 and older. They must have signs of cognitive impairment and be evaluated for Alzheimer's or other decline.
The Alzheimer's Association notes in its Alzheimer's Association news report that PrecivityAD2 is the first cleared Alzheimer's blood test for patients as young as 40. It is not a checkup test for people without symptoms. It fits patients already referred for memory concerns, changes in the 40s and 50s, or later-life decline with an unclear cause.
- age 40 or older
- ongoing memory, language, or thinking symptoms
- clinical evaluation for Alzheimer's or other cognitive decline
What does the blood sample measure?
The test uses high-resolution mass spectrometry in a laboratory. That method measures very small proteins in plasma with high precision. It measures the Aβ42/40 ratio, which compares two amyloid fragments in blood.
It also measures the p-tau217/np-tau217 ratio, which compares two forms of tau. The two ratios are combined into an Amyloid Probability Score 2. That score estimates the chance that amyloid plaques would appear on a PET scan or in spinal fluid.
How well did it match PET or spinal fluid?
NeurologyLive reported on a 1,142-person study in people with symptoms. Compared with amyloid PET or spinal fluid testing, a positive blood result had 97.6% positive predictive value. A negative result had 93.1% negative predictive value, according to NeurologyLive in its NeurologyLive accuracy report.
Positive predictive value means most positive results matched amyloid found by PET or spinal fluid. Negative predictive value means most negative results matched no amyloid on those tests. No test is perfect, so the clinic still weighs symptoms, exams, and history.
How will memory clinics use it?
For clinic patients, C2N describes faster blood-based rule-in or rule-out of amyloid pathology. That result can guide diagnosis and referral to clinical trials. C2N said the FDA-cleared kit version was expected later in 2026.
C2N states the test is not for screening and not a stand-alone diagnosis. It must be used with clinical evaluation. A typical next step is a visit with symptom history, cognitive testing, and review of medicines and other causes. Bring that packet to the visit so the doctor can judge whether the blood test fits.
- bring examples of day-to-day memory changes
- bring a full medicine list
- bring a family member who has seen the changes
- ask what a positive or negative result would change for care or trial referral
