The third cleared test is C2N Diagnostics' PrecivityAD2, cleared August 20, 2026 for adults age 40 and older with signs of cognitive impairment. Primary-care patients avoid overreading it by using it only for evaluated symptoms, with counseling and clinician follow-up, not as a standalone diagnosis.
A blood biomarker test measures proteins in blood that reflect brain change. Here amyloid pathology means abnormal amyloid buildup linked to Alzheimer's disease. A positive signal supports further evaluation, it does not by itself diagnose dementia.
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
- Who is this test for?
- What does the sample measure?
- How accurate is it in evaluated patients?
- How can you avoid overreading the headline?
Who is this test for?
The test is for symptomatic adults age 40 and older being evaluated for Alzheimer's or another cognitive cause. According to the Alzheimer's Association, the FDA clearance covers that symptomatic group in its clearance announcement. It is not cleared for routine screening without symptoms.
It is the first cleared blood test to reach the 40s. Prior tests had age-55 floors, according to AJMC. That change matters for younger symptomatic patients, not for worried but unimpaired adults.
- memory or thinking changes you or family noticed
- documented impairment on history, exam, or cognitive testing
- a clinician evaluating Alzheimer's versus another cause
- counseling before testing about benefits, limits, and next steps
What does the sample measure?
The test uses high-resolution mass spectrometry on plasma. It measures amyloid-beta 42/40 plus percent p-tau217, according to NeurologyLive. Those are blood markers tied to amyloid pathology.
The markers combine into an Amyloid Probability Score 2. The report is negative, positive, or intermediate likely-positive. Each category carries a different level of confidence and needs clinical context.
How accurate is it in evaluated patients?
In a 1,142-person symptomatic validation cohort versus amyloid PET or spinal fluid, the test showed 97.6% positive predictive value and 93.1% negative predictive value, according to NeurologyLive in its test performance summary. Those values apply when symptoms are present and pretest risk is higher.
The middle group needs care. In that study 17.3% fell in likely-positive with only 77.3% positive predictive value. An intermediate result is uncertain, so ask what repeat testing, imaging, or referral your clinician advises.
How can you avoid overreading the headline?
Clearance does not authorize population screening or standalone diagnosis. According to AJMC, the test must supplement clinical history, examination, cognitive testing and sometimes imaging or spinal-fluid testing by an experienced clinician in its coverage guidance. For primary care, do not order or interpret the test without documented impairment and counseling. Positive amyloid does not always mean impending dementia.
False positives can prompt overdiagnosis, extra procedures, worry, and family conflict. Social media often misses that warning. A September 2026 analysis of posts reaching over 114 million followers found more than one-third promoted blood tests for asymptomatic screening, contrary to guidelines, according to Medscape. Only 12% of those mentioned harms such as false positives. Bring the headline to the visit, then decide together whether testing changes care.
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