On August 20, 2026, the FDA cleared PrecivityAD2, a blood test from C2N Diagnostics, for use in adults as young as 40 who are already showing signs of cognitive impairment, according to the Alzheimer's Association. That makes it the first FDA-cleared Alzheimer's blood test available to patients below the age ranges most prior tests targeted, a detail that matters directly to younger-onset Alzheimer's families, as NeurologyLive reported. For families watching a parent, spouse, or sibling develop memory or thinking problems well before the disease's typical late-life onset, this clearance removes one obstacle: a blood test now exists that is cleared to be used on them, not just on patients decades older.
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.
- Check eligibility on Neurologylive’s official study page — Use this page to check the study’s participation requirements.
Table of Contents
- What PrecivityAD2 Actually Measures
- Why the Age-40 Floor Matters for Younger-Onset Families
- How Reliable Is the Result?
- What the Clearance Does Not Cover
- When and How to Access the Test
- Frequently Asked Questions
What PrecivityAD2 Actually Measures
PrecivityAD2 is a blood test that estimates whether amyloid plaque, a protein buildup associated with Alzheimer's disease, is present in the brain. It measures two things in a blood sample: the ratio of two amyloid proteins (Aβ42/40) and the ratio of two forms of a protein called tau (p-tau217/np-tau217), using a lab technique called high-resolution mass spectrometry, according to NeurologyLive. Those two measurements get combined into a single proprietary score.
The result comes back as one of three readings: negative, positive, or "likely positive" for brain amyloid pathology, the biological hallmark doctors look for when diagnosing Alzheimer's disease. This is the third blood-based Alzheimer's biomarker test the FDA has cleared overall. The two before it relied only on the p-tau217 measurement and were limited to older patients, per Practical Neurology. Adding the amyloid ratio alongside p-tau217 is what let C2N Diagnostics seek clearance for a wider, younger age range.
Why the Age-40 Floor Matters for Younger-Onset Families
Younger-onset Alzheimer's (sometimes called early-onset) refers to the disease appearing before age 65. Standard diagnostic pathways, and the blood tests cleared before PrecivityAD2, were built and validated for patients closer to 55 to 65 and older, which routinely delayed diagnosis for younger symptomatic patients, Healio noted. That gap meant a 42-year-old with genuine memory or thinking symptoms often had no cleared blood-based path to an answer — only PET scans, spinal taps, or watching and waiting as symptoms worsened.
PrecivityAD2's clearance down to age 40 closes that specific gap for the first time with an FDA-cleared blood test. It does not mean every 40-year-old with occasional forgetfulness should ask for the test. The clearance covers adults 40 and older who are already presenting with signs or symptoms of cognitive impairment, evaluated by a clinician, not people without symptoms, the Alzheimer's Association specified.
How Reliable Is the Result?
C2N Diagnostics validated PrecivityAD2 in a study of 1,142 people, comparing the blood test's results against amyloid PET scans or spinal fluid testing, the reference standards doctors already trust for confirming amyloid pathology. A positive PrecivityAD2 result matched true amyloid pathology 97.6% of the time, and a negative result correctly ruled out amyloid pathology 93.1% of the time, according to Patient Care Online. Those numbers mean the test is good at confirming a positive and good at ruling out a negative, but neither number is 100%.
A small share of results will still be wrong in either direction, which is one reason the FDA cleared it as an aid to diagnosis alongside clinical evaluation, not as a replacement for a doctor's judgment. The "likely positive" category sits between the two certain outcomes. A clinician who gets that result typically still needs the fuller clinical picture — symptoms, history, and sometimes imaging — before reaching a diagnosis.
What the Clearance Does Not Cover
The FDA's clearance is specific: PrecivityAD2 is authorized for patients who already have cognitive symptoms, used alongside a clinical evaluation. It is not authorized for screening people with no symptoms, and it is not authorized as a standalone diagnostic test on its own, Practical Neurology emphasized. That limitation matters for families hoping to use the test to get ahead of the disease before any symptoms appear — for instance, an adult child of someone with younger-onset Alzheimer's who wants to know their own risk early.
This clearance does not open that door. The test is built for people already showing signs of cognitive impairment, not for asymptomatic risk assessment. A positive or "likely positive" result also does not by itself mean a person has Alzheimer's disease; it indicates amyloid pathology is present, which a clinician then weighs together with symptoms, history, and other findings to reach an actual diagnosis.
When and How to Access the Test
C2N Diagnostics has said the newly FDA-cleared version of PrecivityAD2 is expected to become commercially available later in 2026. In the meantime, the test remains available in its existing form — a lab-developed test validated under CLIA rules — through C2N's own clinical laboratory, according to C2N Diagnostics, via Cortex STL.
For a family pursuing this now, the practical starting point is the same either way: a doctor orders the test for a patient who is already experiencing cognitive symptoms, after an initial clinical evaluation. Families can reasonably ask their neurologist or primary care physician whether PrecivityAD2, in either its current lab-developed form or the newly cleared version once it ships, is appropriate for their situation. The Alzheimer's Disease Drug Foundation, which funded early biomarker research behind the test, has framed the clearance as validation that blood-based testing can offer a faster, less invasive path to an Alzheimer's diagnosis than PET scans or spinal taps, the organization said.
- Confirm the patient is 40 or older and already showing cognitive symptoms — the clearance does not cover screening without symptoms.
- Ask whether the ordering clinic is using the CLIA-validated version now available through C2N's lab, or waiting for the FDA-cleared version later in 2026.
- Expect the result to come back as negative, positive, or likely positive — ask the clinician how that result will be combined with other findings before any diagnosis is made.
Frequently Asked Questions
Can someone without memory symptoms request PrecivityAD2 to check their risk early?
No. The FDA clearance covers adults 40 and older who already show signs or symptoms of cognitive impairment; it is not authorized for screening people without symptoms.
Does a positive PrecivityAD2 result mean a definite Alzheimer's diagnosis?
No. A positive result indicates amyloid pathology is likely present, but the FDA clearance requires it to be used alongside clinical evaluation, not as a standalone diagnosis.
Is PrecivityAD2 available right now?
The CLIA-validated version is currently available through C2N Diagnostics' own clinical laboratory; the newly FDA-cleared version is expected to become commercially available later in 2026.
You Might Also Like
- How 2026 Tau Imaging News May Affect Alzheimer’s Workups: What Is Established and What Remains Uncertain for People With Mild Cognitive Impairment
- The HHS National Alzheimer’s Plan Update for 2026-2035: A 2026 Action Checklist for Family Caregivers
- Tauklarify Tau PET vs Amyloid PET After the 2026 Approval: What Is Established and What Remains Uncertain for People With Mild Cognitive Impairment
