On August 20, 2026, the FDA cleared PrecivityAD2, made by C2N Diagnostics, as the third blood-based biomarker test for Alzheimer's disease — and the first one cleared for use starting at age 40 rather than 55. That lower age floor matters directly to families watching for younger-onset Alzheimer's, according to the Alzheimer's Association. The clearance does not mean the test was built or validated specifically for people in their 40s and early 50s. It means adults in that age range who show signs of cognitive decline can now be tested with it, inside a validation study that was not broken out by age band.
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Table of Contents
- What PrecivityAD2 Is Cleared to Do
- How Accurate Is the Test, and Where Does It Get Less Certain?
- How PrecivityAD2 Fits Among the Four Cleared Blood Tests
- What This Means — and Doesn't Mean — for Younger-Onset Alzheimer's Families
- When and How to Access the Test
- Frequently Asked Questions
What PrecivityAD2 Is Cleared to Do
PrecivityAD2 is a blood test that measures amyloid-related proteins associated with Alzheimer's disease. The FDA cleared it for adults aged 40 and older who already show signs or symptoms of cognitive impairment and are being evaluated for Alzheimer's or another cause of cognitive decline, according to C2N Diagnostics. It is not a screening test for people without symptoms, and it is not meant to stand alone.
The FDA cleared it to be used alongside a clinical evaluation — a doctor's assessment of symptoms, history, and other findings — not as a replacement for that evaluation. The test works through high-resolution mass spectrometry, a lab method that measures the exact mass of specific protein fragments in blood. That sets it apart chemically from the two tests cleared before it, which use immunoassay methods — a different lab technique that detects proteins through antibody binding rather than mass measurement, according to Healio.
How Accurate Is the Test, and Where Does It Get Less Certain?
In C2N's validation study of 1,142 participants, PrecivityAD2 results were checked against amyloid PET scans or spinal fluid testing — the methods doctors already use to confirm amyloid buildup. The test's positive predictive value was 97.6%, meaning a positive result was correct nearly 98% of the time, and its negative predictive value was 93.1%, according to C2N Diagnostics. Those headline numbers come with a notable exception.
About 17.3% of participants landed in an "intermediate/likely positive" category, and within that group the positive predictive value dropped to 77.3%. A result in that middle zone is meaningfully less certain than a clear positive or negative, which matters for how a family and physician interpret it. A separate benchmark published in npj Dementia measured the test against amyloid PET scans using the lab's standard cutoff and reported 91% overall accuracy, with 90% sensitivity (correctly identifying people with amyloid buildup) and 92% specificity (correctly ruling out people without it). These figures describe the test's performance across the full symptomatic study population, not any particular age group.
How PrecivityAD2 Fits Among the Four Cleared Blood Tests
PrecivityAD2 is the third of four Alzheimer's blood biomarker tests the FDA has cleared since May 2025, and each one differs in who it covers and how its accuracy was measured. PrecivityAD2's 40-and-older eligibility is the one clear structural difference among the four. The other three tests all begin eligibility at 55, which excludes most younger-onset Alzheimer's patients from their cleared use entirely.
- Fujirebio's Lumipulse G pTau217/β-Amyloid 1-42 Plasma Ratio was cleared first, on May 16, 2025, for symptomatic adults 55 and older. Its 499-participant study reported a 92% positive predictive value and 97% negative predictive value, per Fierce Biotech.
- Roche's Elecsys pTau181 was cleared second, on October 13, 2025, also for adults 55 and older.
- C2N's PrecivityAD2 was cleared third, on August 20, 2026, and is the only one of the four approved starting at age 40.
- Roche and Eli Lilly's Elecsys pTau217 followed four days later, cleared August 24, 2026, for adults 55 and older. Its four-country, 2,148-person validation matched PET results in 88% of cognitively impaired participants and 91% of cognitively unimpaired participants, according to AJMC.
What This Means — and Doesn't Mean — for Younger-Onset Alzheimer's Families
Younger-onset Alzheimer's, sometimes called early-onset Alzheimer's, refers to disease that begins before age 65. PrecivityAD2's clearance down to age 40 is the first time any FDA-cleared blood biomarker test has reached that part of the younger-onset range at all. That access does not come with age-specific proof of accuracy. No publicly reported figures break out PrecivityAD2's accuracy, sensitivity, or predictive values separately for people aged 40 to 54 — the 1,142-person validation study and the npj Dementia accuracy figures are both reported only for the pooled group of symptomatic adults across all ages tested.
That gap is consistent with the broader research picture. A 2026 analysis from the LEADS consortium, published in Alzheimer's & Dementia and covering 189 early-onset Alzheimer's patients, 52 early-onset non-Alzheimer's patients, and 83 cognitively normal participants, states plainly that minimal prior work has examined plasma biomarkers specifically in early-onset Alzheimer's disease. The same analysis did find that early-onset Alzheimer's participants had more pathological levels of the markers Aβ42/40, p-tau231, and GFAP than early-onset patients with other causes of cognitive decline, after adjusting for cognitive status — a sign that blood markers can distinguish early-onset Alzheimer's from its look-alikes, even without a dedicated accuracy study for PrecivityAD2 in that age group. For a family pursuing a diagnosis in a person in their 40s or early 50s, that means the test is now available to them, but the confidence figures quoted for PrecivityAD2 describe the general symptomatic population the company studied, not a figure proven for their specific age range.
When and How to Access the Test
C2N says the newly cleared version of PrecivityAD2 is expected to reach the market later in 2026. In the meantime, the company's existing CLIA-validated laboratory version — a version run under separate laboratory-certification rules rather than FDA clearance — remains available now through C2N's own clinical lab, according to C2N Diagnostics.
A doctor ordering either version is working from the same underlying blood draw and lab science; the difference is regulatory pathway and availability timing, not a different test. Anyone considering it should ask their physician which version is currently orderable and how an intermediate or borderline result — the 17.3% of cases where predictive value drops to 77.3% — would be handled if it comes back.
Frequently Asked Questions
Does PrecivityAD2 replace a PET scan or spinal fluid test for diagnosis?
No. The FDA cleared it to be used alongside clinical assessment, not as a standalone diagnostic, and C2N's own validation study checked it against PET scans and spinal fluid results rather than replacing them.
What happens if a PrecivityAD2 result comes back "intermediate/likely positive"?
That result occurred in about 17.3% of participants in C2N's validation study, and its positive predictive value was only 77.3% — notably lower than the 97.6% seen for a clear positive result, so it carries more uncertainty.
Is PrecivityAD2 proven accurate for people in their 40s specifically?
No separate accuracy data exists for the 40-54 age group; the reported predictive values and accuracy figures come from the pooled study population across all ages tested.
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