The third FDA-cleared Alzheimer's blood biomarker test in 2026 is C2N Diagnostics' PrecivityAD2, a blood test that measures Alzheimer's-linked proteins to help evaluate cognitive symptoms. Established use is aided evaluation of symptomatic adults 40 and older in primary care, while uncertainty remains for intermediate scores that need PET or spinal-fluid follow-up. FDA cleared PrecivityAD2 on Aug.
20, 2026 as the third cleared blood test and the first for symptomatic adults as young as 40, according to the Alzheimer's Association in its clearance announcement. It does not screen healthy people or give a standalone diagnosis. It helps a clinician weigh Alzheimer's pathology alongside exam and testing.
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 Neurologylive — Use this primary source to verify the official guidance.
Table of Contents
- What the test measures
- How accurate is it for symptomatic patients?
- Who qualifies and how doctors use it
- What remains uncertain in primary care
What the test measures
PrecivityAD2 uses mass spectrometry, a lab method that identifies molecules by weight. It measures the plasma A-beta 42/40 ratio and percent p-tau217, two blood markers tied to amyloid buildup. It combines them into an Amyloid Probability Score 2 from 0 to 100.
A higher score means amyloid pathology is more likely. A lower score means it is less likely. The score guides next steps, not treatment by itself.
How accurate is it for symptomatic patients?
In a 1,142-person symptomatic study against amyloid PET or spinal-fluid testing, positive results had 97.6% positive predictive value and negative results had 93.1% negative predictive value, as NeurologyLive reports in its clearance coverage. That means most clear positives and negatives matched the reference result. These figures apply to people already showing cognitive impairment.
Primary-care accuracy also improved in practice. In a 1,310-patient study with 165 physicians, reported by AJMC, primary-care diagnostic accuracy rose from 65% to 93% after reviewing PrecivityAD2 results. That level matched specialist accuracy in the same study.
Who qualifies and how doctors use it
The cleared use is narrow. It is only for adults 40 and older with signs or symptoms of cognitive impairment. It works as an aid alongside history, exam, and cognitive testing.
In a primary-care visit, expect these checks: Doctors use the result to triage referrals, counseling, and further testing. A clear result can speed decisions. An unclear result points to PET or spinal-fluid testing.
- documented memory, thinking, or functional change
- focused history and physical exam
- brief cognitive testing
- blood draw for biomarker review at a follow-up visit
What remains uncertain in primary care
About 17.3% of results fall in an intermediate likely-positive band. That band had only 77.3% predictive value in validation testing. False positives and false negatives remain possible there. Planning is also shifting.
Being Patient reports in its blood-test guide that Roche Elecsys pTau217 was cleared four days later on Aug. 24, 2026, while C2N said the FDA-cleared PrecivityAD2 kit would arrive later in 2026. Patients should ask which test their clinic offers and what follow-up path it uses. Bring a symptom timeline, medication list, and family history to that visit.
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