On 20 August 2026 the U.S. Food and Drug Administration cleared PrecivityAD2, a blood test from St. Louis–based C2N Diagnostics, to aid evaluation for Alzheimer’s disease in adults aged 40 and older who already show signs or symptoms of cognitive impairment. The clearance is for use with a clinical workup, not instead of one. It is not a stand-alone diagnosis and not a population screen.
In C2N’s clinical validation study of 1,142 adults presenting with cognitive decline, a Positive PrecivityAD2 result had a 97.6% positive predictive value (PPV) for brain amyloid pathology, and a Negative result had a 93.1% negative predictive value (NPV), measured against amyloid PET visual read or cerebrospinal fluid (CSF) biomarkers. A middle “Likely Positive” category appeared in 17.3% of subjects and carried a 77.3% PPV. Those figures speak to amyloid plaque status relative to PET or CSF — not to a clinical dementia label on its own.
The Alzheimer’s Association calls PrecivityAD2 the third FDA-cleared blood-based Alzheimer’s biomarker test, and the first cleared for patients as young as 40. Underlying measurement technology came from Washington University School of Medicine in St. Louis; C2N is a WashU startup that commercialized it.
Why it matters
Getting an Alzheimer’s workup still often means a specialty referral, a PET scan, or a lumbar puncture for CSF. Those tools work. They are also expensive, scarce, or invasive, and many people with early memory complaints never reach them. C2N cites estimates of 19–20 million U.S. adults aged 65 and older living with cognitive impairment, plus hundreds of thousands between 45 and 65, who may benefit from earlier clarification of amyloid status.
Age 40 on the label is the practical news for families dealing with younger-onset cognitive symptoms. Prior FDA-cleared blood Alzheimer’s biomarkers were not cleared that young. Joanne Pike, Alzheimer’s Association president and CEO, framed the extension as recognition that younger-onset Alzheimer’s is a real clinical path, not an afterthought.
WashU Medicine’s Randall J. Bateman and David M. Holtzman, co-founders of C2N, developed key protein-measurement methods behind the assay. Bateman’s point in the WashU release is the operational one: a single blood draw that can flag amyloid pathology associated with Alzheimer’s, so people seeking causes of memory loss can move earlier toward care planning — including, where appropriate, therapies that slow progression and work best when started sooner.
A CLIA-validated PrecivityAD2 offering was already orderable through C2N’s clinical lab. FDA clearance does not invent the assay from scratch. It expands how the company can market the cleared version to clinicians and health systems that treat FDA quality assurance as a gate, and it can ease the path to insurance coverage. C2N says the FDA-cleared version is expected later in 2026; the CLIA test remains available in the meantime.
Key numbers
All performance figures below are from C2N’s FDA clearance materials for the dual-cutoff clinical validation study versus amyloid PET or CSF.
| Metric | Value |
|---|---|
| FDA clearance date | 20 August 2026 |
| Indicated age | ≥40 with cognitive symptoms |
| Validation cohort (n) | 1,142 |
| Positive result — PPV (rule-in) | 97.6% |
| Negative result — NPV (rule-out) | 93.1% |
| Likely Positive share of cohort | 17.3% |
| Likely Positive — PPV | 77.3% |
| Reference standards | Amyloid PET visual read or CSF biomarkers |
| Analytes → score | Aβ42/40 + %p-tau217 → APS2 (0–100) |
| Platform | High-resolution mass spectrometry |
| Alzheimer’s Association rank | 3rd FDA-cleared AD blood biomarker; 1st from age 40 |
C2N also reports consistent performance with increasing age and across 12 pre-specified chronic conditions common in aging (including atrial fibrillation, chronic kidney disease, diabetes, depression, obesity, and history of stroke or TIA). That is a reliability claim in comorbid adults, not a claim that the test diagnoses those conditions.
How it works
PrecivityAD2 is an in vitro blood test that uses high-resolution mass spectrometry (HRMS) to quantify specific plasma β-amyloid and tau peptide isoforms in one sample. The lab reports an Aβ42/40 ratio and a phosphorylated-to-non-phosphorylated p-tau217 ratio (%p-tau217). Those two ratios feed a proprietary algorithm that produces an Amyloid Probability Score 2 (APS2) from 0 to 100, which maps to Positive, Likely Positive, or Negative categories for the likelihood of amyloid pathology linked to Alzheimer’s disease.
WashU notes that, unlike some other FDA-cleared Alzheimer’s blood tests that rely on immunoassay methods, PrecivityAD2’s cleared path is mass-spectrometry–based quantitative measurement. C2N describes HRMS as a clinical-lab gold standard for sensitive, specific protein quantification from blood. The clinical claim is aid in identifying amyloid pathology, interpreted alongside history, exam, and other diagnostics — the same framing the Alzheimer’s Association uses for blood biomarkers in specialty care.
Ordering is limited to health care professionals experienced in evaluating cognitive impairment. That gate is intentional: the product is built for the diagnostic pathway, not for a consumer kit or a wellness panel.
What this is not
- Not a stand-alone Alzheimer’s diagnosis. The FDA indication and both C2N and the Alzheimer’s Association state the test is used with clinical assessment. There is still no single blood result that equals a full diagnosis.
- Not a population screen. It is indicated for adults with signs or symptoms of cognitive impairment who are already being evaluated — not for asymptomatic mass testing.
- Not “dementia yes/no.” The published PPV/NPV are against amyloid PET or CSF, which mark plaque pathology. Amyloid pathology is a hallmark of Alzheimer’s disease biology; it is not identical to a clinical dementia syndrome by itself.
- Not the first blood Alzheimer’s biomarker ever cleared. The Association says it is the third. The novelty here is clearance down to age 40, plus the HRMS / multi-analyte APS2 design C2N emphasizes.
- Not brand-new science dropping into clinics overnight. A CLIA PrecivityAD2 was already in use. Clearance mainly widens marketing, quality-assurance signaling, and potential coverage for the FDA-cleared version expected later this year.
What to watch
- When the FDA-cleared kit actually ships. C2N says later in 2026. Until then, the CLIA offering is the one clinics can already order.
- Coverage. WashU flags that clearance can facilitate insurance payment. Payer policies will decide whether PrecivityAD2 becomes routine workup or remains a specialty add-on.
- How “Likely Positive” is handled. At 77.3% PPV, that band is medically informative but not a near-certain rule-in. Expect more PET/CSF and specialty follow-up in that group — and watch whether real-world pathways treat it as escalate, watch, or both.
- Guideline uptake. The Alzheimer’s Association has clinical practice guidelines for blood biomarker use in specialty settings and says they are updated as evidence moves. Specialty vs primary-care deployment will matter more than the press release.
- Treatment timing. Amyloid-targeting therapies exist and are more useful earlier; C2N cites real-world work suggesting stacking multiple biomarker confirmations can delay treatment starts. Whether a high-performing blood step shortens that path is an outcomes question, not settled by clearance day alone.
Sources
- C2N Diagnostics, “FDA Clears C2N Diagnostics’ PrecivityAD2® — First Alzheimer’s Blood Test for Adults with Cognitive Symptoms as Young as 40,” 20 August 2026 — https://c2n.com/news-releases/bg2ziqcz39o3wxf5uc04u279ziw0yv
- Alzheimer’s Association, “Statement on FDA Clearance of PrecivityAD2 Blood Test for Alzheimer’s Diagnosis in Adults as Young as 40,” 20 August 2026 — https://www.alz.org/news/2026/fda-clearance-precivityad2-blood-test-alzheimers
- WashU Medicine, “FDA clears blood test to aid evaluation for Alzheimer’s disease” (Shawn Ballard), 21 August 2026 — https://medicine.washu.edu/news/fda-clears-blood-test-to-aid-evaluation-for-alzheimers-disease/
