The third FDA-cleared Alzheimer's blood biomarker test is C2N Diagnostics' PrecivityAD2, cleared on Aug. 20, 2026, as the Alzheimer's Association reports in its clearance announcement.
A blood biomarker test measures Alzheimer's-related proteins in blood to help assess amyloid buildup in the brain. Before 2025 the category had no cleared tests. PrecivityAD2 now gives memory clinics a blood-based option for initial assessment of symptomatic adults.
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 Alz — Use this primary source to verify the official guidance.
- Read the official guidance from C2N — Use this primary source to verify the official guidance.
Table of Contents
- Who can get this test?
- How does the test work?
- How accurate is it, and where is the gray zone?
- What should you do at your memory clinic visit?
Who can get this test?
The test is for adults age 40 and older with signs or symptoms of cognitive impairment, as C2N Diagnostics states in its company announcement. It is the first cleared Alzheimer's blood test available to symptomatic patients in their 40s.
That focus matters for younger-onset concerns. Memory loss, confusion with familiar tasks, word-finding trouble, or a family-noted change in thinking are the kinds of symptoms to bring to the visit.
How does the test work?
The lab uses high-resolution mass spectrometry to measure two plasma ratios: Aβ42/40 and p-tau217/np-tau217. It combines both into an Amyloid Probability Score 2 from 0-100.
A higher score signals a higher likelihood of brain amyloid. For clinic patients, a single blood draw can substitute for initial PET or lumbar puncture assessment.
How accurate is it, and where is the gray zone?
In 1,142 symptomatic adults, the test showed 97.6% positive and 93.1% negative predictive value versus amyloid PET or cerebrospinal fluid, as NeurologyLive describes in its test performance summary. Those values supported clearance validation.
The limit is the middle result. About 17.3% of patients fell in an intermediate "likely positive" band with only 77.3% positive predictive value. That result is not a yes or no and needs further workup.
What should you do at your memory clinic visit?
FDA cleared the test only as an aid alongside history, exam, cognitive testing, and clinician judgment, according to the American Journal of Managed Care in its coverage of the clearance. It is not for screening without symptoms and not a standalone diagnosis. Ask your clinician what an intermediate score would mean for you before you give blood.
- Bring symptom dates, daily-life examples, medications, and a family observer
- Ask how your clinic handles intermediate scores
- Ask if a result could speed treatment decisions or trial referral
