PrecivityAD2 is a blood test that can support a 2026 Alzheimer's workup, but it cannot answer the question on its own, and a "likely positive" result needs a specific explanation before a person with mild cognitive impairment (MCI) acts on it. The FDA cleared PrecivityAD2 on August 20, 2026, for adults 40 and older who already show signs of cognitive impairment, including MCI or dementia — not for people without symptoms. This test, made by C2N Diagnostics, is meant to work alongside a clinician's exam, not replace it. The sections below walk through what the three possible results mean, why the middle category deserves extra scrutiny, and what questions to bring to a follow-up appointment.
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 PrecivityAD2 Actually Measures
- How Reliable Is Each Result Category?
- What a "Likely Positive" Result Should Prompt You to Ask
- Should You Expect to Be Retested?
- Who Should Be Cautious About the Result's Accuracy
- Frequently Asked Questions
What PrecivityAD2 Actually Measures
PrecivityAD2 draws a blood sample and measures two biomarkers tied to Alzheimer's pathology: the ratio of amyloid-beta 42 to amyloid-beta 40, and the percentage of phosphorylated tau217 (%p-tau217). A mass spectrometry lab combines both readings into a single number called the Amyloid Probability Score 2, or APS2, according to Mayo Clinic Laboratories' test catalog. The APS2 estimates how likely it is that amyloid plaques — one of the hallmark proteins seen in Alzheimer's disease — are present in the brain.
It does this without the radiation, cost, or scheduling burden of an amyloid PET scan, and without the lumbar puncture a cerebrospinal fluid (CSF) test requires. Unlike the original PrecivityAD, which reported a two-tier result, PrecivityAD2 sorts people into three categories: negative, "likely positive," and positive, per NeurologyLive's coverage of the FDA clearance. That middle category is new, and it is the one that most often confuses people reading their own lab report.
How Reliable Is Each Result Category?
The reliability of PrecivityAD2 is not uniform across its three categories, and that difference matters more than any single headline accuracy number. In the pivotal study of 1,142 symptomatic adults, researchers compared blood results against amyloid PET or CSF testing — the recognized reference standards — and found a positive PrecivityAD2 result had a 97.6% positive predictive value, while a negative result had a 93.1% negative predictive value, according to Practical Neurology's report on the FDA clearance. In plain terms: a clear positive or clear negative result is right the large majority of the time. The "likely positive" category is a different story.
It showed up in about 17.3% of the study's participants, and it carried only a 77.3% positive predictive value, per C2N Diagnostics' Businesswire announcement. That means roughly one in four people who land in this band do not actually have confirmed amyloid pathology when checked against PET or CSF. For someone with MCI, this distinction changes how much weight the result should carry. A clear positive or negative can reasonably anchor a conversation about next steps. A "likely positive" is a signal to keep investigating, not a settled answer.
What a "Likely Positive" Result Should Prompt You to Ask
Anyone who receives a "likely positive" result should ask their clinician what additional testing is needed before treatment decisions are made. Because roughly a quarter of people in this band do not have confirmed amyloid pathology, the result alone is not strong enough evidence on its own. It helps to know this uncertainty is not new to this test family.
For the original PrecivityAD, a 2022 review in American Family Physician found that 10-15% of patients fell into an intermediate score band with unclear clinical meaning, and the review warned that the absence of guidance for that range could add to patient anxiety, per American Family Physician. PrecivityAD2's own published guidance for interpreting its "likely positive" band specifically was not available in the sources reviewed for this article, which is itself a reason to raise the question directly with the ordering clinician rather than assume the newer test has resolved it. Questions worth bringing to that appointment include:.
- Does this result change the recommendation for a confirmatory PET scan or CSF test?
- How does my result fit with my cognitive testing and symptom history?
- Is there a reason to wait and reassess, or to move forward with further workup now?
- What would change if the confirmatory test disagrees with the blood result?
Should You Expect to Be Retested?
PrecivityAD2 is not built for repeat or serial testing. C2N states that the FDA-cleared version is not intended to be used as a standalone diagnostic, for screening people without symptoms, or for tracking disease progression or treatment response through repeated testing, according to Practical Neurology. That restriction matters for anyone wondering whether a second draw a few months later would clarify an ambiguous result.
A Journal of Alzheimer's Disease paper examining intermediate scores on the original PrecivityAD test states plainly that the value of retesting after an indeterminate result is unknown, and it calls for a longitudinal study before any recommendation on whether or when to retest can be made, per the Journal of Alzheimer's Disease. No comparable retesting guidance for PrecivityAD2's "likely positive" category appears in the available sources. In practice, this means a "likely positive" result is resolved through a different, confirmatory test — PET or CSF — rather than through drawing blood again later and hoping for a clearer number.
Who Should Be Cautious About the Result's Accuracy
Two groups should treat their PrecivityAD2 result with extra caution, regardless of which category it falls into. Mayo Clinic Laboratories notes that reduced kidney function from chronic kidney disease, or from obesity, can lower the amount of amyloid peptides cleared into the blood, which can affect the test's accuracy in people with either condition, according to Mayo Clinic Laboratories. The same source also notes that the performance data behind the test come predominantly from a White U.S.
population, so how accurately the test performs across other racial or ethnic groups is not yet firmly established. Anyone in either situation — a kidney condition, obesity, or a background outside the population the validation study drew from — has a reason to ask their clinician how much weight to put on the blood result specifically, independent of the "likely positive" question discussed above. Mayo Clinic Laboratories is explicit that the result, whatever the category, does not by itself establish or rule out an Alzheimer's diagnosis; it has to be read alongside a full clinical evaluation of symptoms, history, and cognitive testing.
Frequently Asked Questions
Can PrecivityAD2 confirm an Alzheimer's diagnosis on its own?
No. Mayo Clinic Laboratories states the result must be interpreted alongside a full clinical evaluation, not used alone to confirm or rule out the diagnosis.
Is PrecivityAD2 approved for people without memory symptoms?
No. The FDA clearance covers adults 40 and older who already show signs or symptoms of cognitive impairment, including MCI or dementia.
Why does the "likely positive" category get extra scrutiny?
Because about one in four people in that band did not have confirmed amyloid pathology in the pivotal study, compared with much higher accuracy for clear positive or negative results.
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