PrecivityAD2 is a blood test that estimates the likelihood of Alzheimer's-related amyloid in the brain. In 2026 it was cleared for adults 40 and older with cognitive symptoms, but it cannot diagnose Alzheimer's alone. C2N Diagnostics announced the FDA clearance on Aug.
20, 2026 for adults 40 and older with signs of impairment. Details appear in the C2N Diagnostics announcement. Adults with new memory symptoms still need a clinician-led workup rather than a direct-to-consumer answer.
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.
Table of Contents
- What the test measures
- Why diagnosis before 65 often takes longer
- What the scores get right and where they blur
- How to act on new symptoms without overreading
What the test measures
Amyloid buildup is a brain change linked to Alzheimer's disease. The test uses high-resolution mass spectrometry to measure two blood markers, plasma Aβ42/40 and percent p-tau217.
It combines both ratios into an Amyloid Probability Score 2 from 0 to 100. C2N Diagnostics describes the score as an indicator of likely brain amyloid pathology.
Why diagnosis before 65 often takes longer
The Alzheimer's Association defines younger-onset Alzheimer's as disease affecting people under 65. It notes diagnosis is often difficult and age or history can lead to repeated misdiagnosis and incorrect treatment. AJMC reporting notes clinicians often first attribute cognitive complaints in the 40s and 50s to depression, sleep loss or menopause.
Those conditions are far more common than early-onset Alzheimer's. Recognition can lag until work performance or household finances show clear dysfunction. A blood test does not erase that timing problem. Amyloid information helps most once a clinician has mapped symptoms, function and other causes.
What the scores get right and where they blur
NeurologyLive reported results in 1,142 symptomatic adults compared against amyloid PET or spinal-fluid testing, with details in the NeurologyLive report. Positive results showed 97.6% positive predictive value and negative results showed 93.1% negative predictive value. About 17.3% of participants fell into an intermediate "likely positive" group.
For that group, positive predictive value was only 77.3%. That gray zone is the main reason to avoid treating one phrase as proof. The Alzheimer's Association states the test is indicated only alongside assessment by professionals experienced in cognitive impairment, as explained in the Association's clearance summary. It is not cleared as population screening or a stand-alone diagnosis.
How to act on new symptoms without overreading
AJMC reporting advises adults with new memory symptoms to seek full evaluation with history, exam and cognitive testing. When indicated, that workup can include brain imaging or spinal-fluid testing. AJMC notes PrecivityAD2 aids amyloid confirmation and care and trial planning, not self-interpreted proof of Alzheimer's.
Bring specifics, not conclusions. Use the visit to make causes easier to sort out. Ask the clinician what result range would prompt another test and what would not. Bring a dated symptom log and a full medication list to that first visit.
- examples with dates, such as missed meetings, unpaid bills or wrong turns on familiar routes
- sleep, mood, medications, alcohol use, thyroid history and, when relevant, menopause history
- questions about cognitive testing, imaging or referral to a memory specialist
- what an amyloid result would change for care planning or trial options
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