PrecivityAD2 is a blood test that measures amyloid-related proteins to help doctors evaluate adults who already have symptoms of cognitive decline. The FDA cleared it on August 20, 2026 for adults 40 and older with signs of cognitive impairment, making it the first FDA-cleared Alzheimer's blood test to reach that age, and the first blood test of its kind usable in the workup for younger-onset Alzheimer's, according to C2N Diagnostics' announcement. The test does not diagnose Alzheimer's on its own. The FDA's clearance limits PrecivityAD2 to use alongside a full clinical evaluation, and explicitly excludes screening people with no symptoms or using the result as a standalone diagnosis, according to the same C2N announcement.
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 measures and why the age 40 floor matters
- How accurate is the test, and what do the numbers mean for a result?
- Why an adjunct test, not a standalone diagnosis
- What this means in practice for younger-onset families
What PrecivityAD2 measures and why the age 40 floor matters
PrecivityAD2, made by C2N Diagnostics, analyzes plasma biomarkers linked to amyloid buildup in the brain, one of the hallmark changes seen in Alzheimer's disease. The FDA's August 2026 clearance applies to symptomatic adults starting at age 40, a notable drop from where blood-based Alzheimer's testing stood even a year earlier, according to C2N's announcement. That age range matters directly to families dealing with younger-onset Alzheimer's, where symptoms appear before age 65. Fujirebio's Lumipulse G test, the first FDA-cleared Alzheimer's blood test, was cleared in May 2025 but limited to adults 55 and older, leaving no FDA-cleared blood test option for people in their 40s and early 50s showing symptoms, according to Healio's coverage of the clearance.
PrecivityAD2 is the first to close part of that gap. The age floor did not move in one step. C2N had already lowered its own intended-use threshold to 50 in August 2025 based on additional validation data the company reported, before the FDA's broader clearance pushed it down to 40, according to C2N's 2025 announcement. Each step applies only to adults who already have cognitive symptoms under evaluation, not to people checking their risk preventively.
How accurate is the test, and what do the numbers mean for a result?
The FDA's clearance decision rested on a study of 1,142 adults, comparing PrecivityAD2's plasma result against amyloid-PET imaging or cerebrospinal fluid (CSF) biomarkers as the reference standard. The test's positive result carried a 97.6% positive predictive value and its negative result carried a 93.1% negative predictive value, according to C2N's announcement. In plain terms, a clear positive is very likely to reflect real amyloid pathology, and a clear negative is very likely to reflect its absence. Not every result lands in a clear category.
The same study found 17.3% of participants fell into an intermediate "likely positive" range, where the positive predictive value dropped to 77.3%, according to C2N's announcement. A result in that middle band is meaningfully less certain than a clear positive or negative, and on its own does not settle the question. Separate validation work supports the same overall picture. A 2025 study published in npj Dementia reported 91% overall accuracy, 90% sensitivity, and 92% specificity against amyloid-PET imaging, which C2N says meets the Alzheimer's Association's 2025 benchmark of 90% accuracy or higher for a confirmatory blood biomarker test, according to C2N's research summary. A JAMA study of more than 1,200 patients in Sweden found accuracy above 90% as well, with performance in primary care matching specialized memory clinics, according to C2N's summary of the JAMA findings.
Why an adjunct test, not a standalone diagnosis
The FDA's clearance language is specific: PrecivityAD2 is meant to be used alongside a full clinical assessment, not in place of one, and it is not cleared for screening people with no symptoms, according to C2N's announcement. That distinction matters for a family hoping a blood draw alone will settle whether a younger relative's memory changes are Alzheimer's. A geriatrician interviewed about the test's clinical role put the limit plainly: a positive blood result by itself cannot justify starting anti-amyloid treatment, and still needs confirmation through PET imaging or a lumbar puncture for CSF testing before a diagnosis is finalized, according to a SUNY Upstate Medical University podcast interview.
The same source warned that treating a blood result as sufficient on its own risks pushing patients into unnecessary downstream procedures. Clinical reviewers add another layer of caution. A review in Practical Neurology notes that blood-biomarker accuracy can be affected by conditions such as kidney disease and heart failure, and that any intermediate or indeterminate result still requires confirmatory testing before it can anchor a diagnosis, according to the Practical Neurology review. For a younger patient with other health conditions, that caveat is worth raising directly with the ordering physician.
What this means in practice for younger-onset families
For a family facing symptoms in a relative in their 40s or early 50s, PrecivityAD2 offers a blood-based option that did not exist under the earlier Lumipulse clearance, which started at age 55, according to Healio's coverage. It can be ordered as part of a workup for someone already showing cognitive symptoms, not as a general risk check for someone without symptoms.
A practical path looks like this: A positive or "likely positive" result is a reason to move toward confirmatory testing and a specialist discussion, not a reason to start treatment on the blood result alone, per the geriatrician's caution in the SUNY Upstate interview. That sequence applies the same way at age 42 as it does at age 72.
- Confirm the person has documented cognitive symptoms under active evaluation — the clearance does not cover symptom-free screening.
- Expect the blood result to sit alongside other findings, not replace them; ask the ordering clinician how a "likely positive" result, specifically, would be followed up.
- If the result is intermediate or the clinical picture is unclear, ask whether amyloid-PET imaging or a CSF test is the next step, since both remain the confirmatory standard.
- Flag any kidney disease, heart failure, or other relevant condition to the clinician, since these can affect how the blood result should be read.
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