PrecivityAD2 is a blood test that helps clinicians evaluate adults aged 40 and older who show signs of cognitive impairment during an Alzheimer's workup. The FDA cleared it on August 20, 2026, making it the first blood-based Alzheimer's test cleared for patients this young, and it is meant to be used alongside a clinician's own assessment rather than in place of one, according to the Alzheimer's Association. For someone with mild cognitive impairment weighing their options, that timing matters. PrecivityAD2 gives a less invasive first comparison point against a spinal tap or a brain scan, before anyone decides whether a more invasive confirmatory test is still needed.
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 Accurate Is the Result for Someone With Mild Symptoms?
- Comparing PrecivityAD2, PET Scans, and Spinal Fluid Testing
- What the Cost Picture Looks Like
- Getting Access to the Test Now
- Frequently Asked Questions
What PrecivityAD2 Actually Measures
PrecivityAD2 is made by C2N Diagnostics and runs on a standard blood draw. The test measures two pairs of proteins in plasma — the Aβ42/40 ratio and the p-tau217/np-tau217 ratio — using high-resolution mass spectrometry, then combines the results into a single number called the Amyloid Probability Score 2, or APS2, scored from 0 to 100, according to Practical Neurology.
A higher APS2 score flags a higher likelihood that amyloid plaques — one of the two hallmark brain changes in Alzheimer's disease — are present. The test does not diagnose Alzheimer's by itself; it estimates the probability of underlying amyloid pathology, which a clinician then weighs alongside the person's symptoms, history, and other findings.
How Accurate Is the Result for Someone With Mild Symptoms?
The clearance rested on a validation study of 1,142 people. A positive PrecivityAD2 result carried a 97.6% positive predictive value for amyloid pathology, and a negative result carried a 93.1% negative predictive value, measured against amyloid PET visual reads or cerebrospinal fluid (CSF) testing as the reference standard, according to Washington University School of Medicine. Washington University researchers specifically report that the test performs comparably to a lumbar puncture or an amyloid PET scan even in patients with only mild cognitive symptoms — the exact group this test is positioned for.
That makes a positive or negative blood result a reasonably reliable first signal before anyone schedules a more invasive procedure. A result still has to be read by a clinician experienced in evaluating cognitive impairment. The FDA-cleared labeling states plainly that PrecivityAD2 is not a screening test and not a stand-alone diagnostic test, so a positive APS2 score prompts further clinical interpretation rather than an automatic diagnosis, per C2N Diagnostics.
Comparing PrecivityAD2, PET Scans, and Spinal Fluid Testing
People evaluating memory or thinking changes typically have three ways to check for amyloid pathology: a blood test like PrecivityAD2, a CSF test drawn by lumbar puncture, or an amyloid PET brain scan. Here is how they differ for someone being evaluated now: Because PrecivityAD2 is designed to be used before a scan or spinal tap is ordered, it functions as a filter: a clear negative may reduce the need for a more invasive follow-up, while a positive result can support the decision to pursue PET or CSF confirmation when the clinical picture calls for it.
- **PrecivityAD2 (blood draw):** Least invasive; cleared for adults 40 and older with signs of cognitive impairment; comparable accuracy to PET or CSF in people with mild symptoms, per Washington University researchers.
- **CSF testing (lumbar puncture):** Requires a spinal needle procedure; has long served as a reference standard for confirming amyloid status.
- **Amyloid PET scan:** A brain imaging procedure that historically costs thousands of dollars per scan and has not typically been reimbursed by Medicare or most insurers, a barrier noted in a PMC-indexed economic review.
What the Cost Picture Looks Like
A peer-reviewed economic model built around a hypothetical health plan of 1 million members found that adopting PrecivityAD2 as an early step in the diagnostic pathway cut total Alzheimer's evaluation costs by 26.2%, a net savings of $10.9 million, or $0.91 per member per month, compared with usual care that relies on PET or CSF testing first, according to a PMC-indexed study. The savings came from reducing how often downstream confirmatory scans were needed.
That modeled savings lines up with the access problem PET scans create on their own. Amyloid PET's lack of routine reimbursement by Medicare and most insurers has long kept it out of reach for many patients, which is part of why a blood-based first step like PrecivityAD2 was designed to sit ahead of it in the evaluation sequence, per the same economic review.
Getting Access to the Test Now
The FDA-cleared version of PrecivityAD2 was expected to reach the market later in 2026. In the meantime, C2N's existing laboratory-developed version of the test — validated under CLIA rules — remained available through C2N's own clinical laboratory, according to Practical Neurology.
A person with mild cognitive impairment who wants to use PrecivityAD2 as part of a 2026 evaluation should ask their clinician two things: whether the clinic can order the CLIA-validated version now, and whether the FDA-cleared version has since become available through their lab network. Either way, the Alzheimer's Association's guidance stands — the test result is one input a clinician experienced in cognitive evaluation interprets alongside the rest of the exam, not a stand-alone answer.
Frequently Asked Questions
Can PrecivityAD2 replace a PET scan or spinal tap entirely?
Not necessarily. Its labeling states it is not a stand-alone diagnostic test, so a clinician may still order PET or CSF testing depending on the result and the clinical picture, per C2N Diagnostics.
Who is eligible for the FDA-cleared version of PrecivityAD2?
Adults aged 40 and older who show signs or symptoms of cognitive impairment and are undergoing evaluation for Alzheimer's disease, per C2N Diagnostics' August 20, 2026 announcement.
How does PrecivityAD2 compare to earlier blood-based Alzheimer's tests?
The Alzheimer's Association identifies it as the third FDA-cleared blood-based biomarker test for Alzheimer's disease, and the first cleared for patients as young as 40, per the Alzheimer's Association.
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