The Food and Drug Administration cleared C2N Diagnostics' PrecivityAD2 blood test on Aug. 20, 2026, to help diagnose Alzheimer's disease alongside standard clinical evaluation. Adults with new memory symptoms avoid overreading the headline by treating it as a doctor-ordered aid, not home screening or a stand-alone diagnosis.
C2N Diagnostics announced the clearance for use together with standard clinical workup in its company announcement. The FDA 510(k) summary K253240 limits the cleared use to adults age 40 and older with signs of cognitive impairment under evaluation. That symptomatic-evaluation frame is the key guardrail for readers seeing social posts about a simple Alzheimer's blood test. Memory change alone does not qualify you; a clinician must judge that workup for decline is appropriate.
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:
- Explore the official data from FDA — Use this primary source to review the underlying data.
- Read the official guidance from C2N — Use this primary source to verify the official guidance.
Table of Contents
Who can use it
PrecivityAD2 is the first FDA-cleared Alzheimer's blood test indicated down to age 40. The Alzheimer's Association notes earlier Lumipulse and Elecsys pTau181 clearances were limited to ages 55 and older in its 2026 test summary. The same Association summary dates Lumipulse to May 2025 and Elecsys pTau181 to October 2025. Clearance does not create a yearly check for worried but unimpaired adults.
Under the FDA summary, it covers people already showing impairment who are being evaluated for decline. A 42-year-old with progressing word-finding trouble in clinic differs from a 42-year-old seeking reassurance without symptoms. The lower age cutoff matters most for early-onset concerns and family-history anxiety. It widens access to evaluation, but symptoms and clinical context still decide testing.
What the test measures
The test uses high-resolution mass spectrometry to measure Alzheimer-related proteins in plasma. In plain terms, the lab identifies tiny protein fragments by weight with high precision. NeurologyLive reports the test quantifies plasma A-beta 42/40 and percent p-tau217 ratios.
A-beta 42/40 reflects amyloid buildup, while p-tau217 reflects tau changes linked to Alzheimer's. The same report says the test combines both into an Amyloid Probability Score 2 from 0 to 100. Higher scores signal higher likelihood of brain amyloid pathology, not a dementia stage.
How accurate is it?
In 1,142 symptomatic adults compared against amyloid PET or spinal-fluid testing, accuracy was high. NeurologyLive reports 97.6 percent positive predictive value and 93.1 percent negative predictive value for brain amyloid in its test performance report. Positive value means a positive result usually matched PET or spinal-fluid evidence; negative value means a negative result usually ruled it out.
The gray zone matters: about 17.3 percent fell in an intermediate likely-positive group. In that group, positive predictive value was only 77.3 percent, NeurologyLive reports. A non-negative result there still needs clinical judgment and possible confirmatory workup.
What to do about new symptoms
The FDA position, summarized via Medical Xpress, is that the test aids experienced clinicians in finding amyloid pathology. It is not intended as population screening or a stand-alone Alzheimer's diagnosis, especially without symptoms. If memory lapses are new, frequent, or worsening, book a clinical visit rather than seeking a blood test alone.
Bring examples, medications, sleep changes, and a person who knows you well. C2N, via BioSpace, expected the FDA-cleared kit later in 2026 while its laboratory version remained available. Newly symptomatic adults should therefore seek clinician evaluation and ordered testing rather than self-screening.
- Ask whether cognitive testing and reversible causes should come first.
- Ask whether an ordered Alzheimer's blood test fits your case.
- Ask what a negative, positive, or intermediate score would change.
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