PrecivityAD2, made by C2N Diagnostics, became the third FDA-cleared blood test for Alzheimer's-related brain changes when the agency cleared it on August 20, 2026, following Fujirebio's Lumipulse in May 2025 and Roche/Eli Lilly's Elecsys pTau181 in October 2025, according to the Alzheimer's Association. For someone with mild cognitive impairment (MCI) — a stage where memory or thinking problems are noticeable but don't yet stop daily independence — the test reports a single number meant to show whether amyloid plaque, a protein linked to Alzheimer's, is likely present in the brain. That number comes with real statistical strength, but it answers a narrower question than most people expect. It says something about brain chemistry, not about whether MCI will turn into dementia or when.
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 original research from NIH — Use this page to review the original research.
- Read the official notice from C2N — Use this primary source to verify the official announcement.
Table of Contents
- What PrecivityAD2 Actually Measures
- How Accurate Is a Positive or Negative Result?
- Why a Clean Result Still Carries Some Uncertainty
- What a Positive Result Does and Doesn't Mean for MCI
- A Note on Which Version of the Test You're Getting
- Frequently Asked Questions
What PrecivityAD2 Actually Measures
PrecivityAD2 uses mass spectrometry, a lab technique that measures the precise weight of molecules, to combine two blood markers: %p-tau217 and the Aβ42/40 ratio. Those two values feed into a single score called the Amyloid Probability Score2, or APS2, which runs from 0 to 100, according to C2N Diagnostics and the Alzheimer's Drug Discovery Foundation.
The test is cleared as an adjunct — a supporting tool used alongside clinical evaluation — not a stand-alone diagnostic or screening test, per the same ADDF announcement. A doctor orders it for a patient who already has symptoms, not to screen someone with no complaints. The clearance also applies to a wider group than earlier tests: adults 40 and older who show signs of cognitive impairment, the youngest starting age of any cleared blood-based Alzheimer's test so far, according to C2N Diagnostics' press release.
How Accurate Is a Positive or Negative Result?
In the clinical validation study behind the clearance, which included 1,142 patients with cognitive symptoms, a positive APS2 result had a 97.6% positive predictive value, and a negative result had a 93.1% negative predictive value, measured against amyloid PET scans and spinal fluid testing as the reference standard, according to the ADDF's summary of C2N's validation data. In plain terms, a positive result was confirmed by PET or spinal fluid testing about 98 times out of 100, and a negative result held up about 93 times out of 100.
Mayo Clinic Laboratories reports APS2 using one cut point rather than the three-zone system used in the original PrecivityAD test. Scores from 0 to 47 are reported negative, meaning a lower likelihood of brain amyloid, and scores from 48 to 100 are reported positive, according to Mayo Clinic Laboratories' test catalog. The earlier version had an "intermediate" zone, roughly 36 to 57, covering about 14% of results that could not be classified as either positive or negative.
Why a Clean Result Still Carries Some Uncertainty
Removing the intermediate zone made PrecivityAD2 easier to read, but it did not remove the uncertainty that zone represented — it just folded that uncertainty into the two existing categories. A sensitivity analysis in the validation study found that if the old intermediate-zone boundaries were applied to APS2 scores, 9.6% of patients, or 56 of the 1,142 studied, would have landed in that indeterminate range, and only 53.6% of those patients actually had amyloid pathology, according to the peer-reviewed validation study on PMC.
That means a small share of people now get a definite positive or negative label on a score that, under the older system, would have been flagged as too close to call. For a person with MCI sitting near the 47/48 cut point, the single clean label on the lab report does not erase that underlying ambiguity — it only hides it from view. Asking the ordering clinician how close a result sits to the cutoff is a reasonable question before treating the label as final.
What a Positive Result Does and Doesn't Mean for MCI
A positive PrecivityAD2 result tells a person with MCI that amyloid pathology is likely present in the brain. It does not by itself confirm that Alzheimer's disease is causing their current symptoms, and it does not predict how soon, or whether, their MCI will progress to dementia, according to C2N Diagnostics and the ADDF.
Clinicians are directed to combine the score with cognitive testing, medical history, and sometimes other biomarkers before counseling a patient on what the result means for their outlook. Clinical reviewers at Alzforum state that tests like this one should currently only be ordered for people who already show cognitive impairment — such as those with MCI or dementia — not used to screen people without symptoms, according to Alzforum's coverage of the clearance. A few practical questions worth asking the ordering clinician:.
- Is my APS2 score close to the 47/48 cut point, or well on one side of it?
- Does a positive result change my current treatment plan, or only confirm a risk factor?
- What other testing — cognitive exams, imaging, history — is being used alongside this score?
- Does a negative result rule out Alzheimer's, or only make amyloid pathology less likely?
A Note on Which Version of the Test You're Getting
C2N's FDA-cleared version of PrecivityAD2 was expected to launch later in 2026. Until that launch, C2N's existing laboratory version — run under separate laboratory rules rather than the new FDA clearance — remained the version available to order, according to the ADDF's announcement. Someone ordering the test now has reason to ask their clinician or lab which version is being used, since interpretation guidance tied specifically to the FDA label may not yet apply to results from the lab-based version.
Frequently Asked Questions
Does a positive PrecivityAD2 result mean I have Alzheimer's disease?
No. It indicates amyloid pathology is likely present, but a clinician combines it with cognitive testing and history before attributing symptoms to Alzheimer's, according to C2N Diagnostics and the ADDF.
Is PrecivityAD2 meant for people without memory symptoms?
No. Alzforum states these tests should currently be ordered only for people already showing cognitive impairment, not for screening people without symptoms.
How is PrecivityAD2 different from the original PrecivityAD test?
PrecivityAD2 combines %p-tau217 and the Aβ42/40 ratio into one APS2 score and is reported with a single cut point, while the original test had a three-zone system with an unclassified "intermediate" range, per Mayo Clinic Laboratories.
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