FDA Clears PrecivityAD2, First Alzheimer Disease Blood Test Available to Symptomatic Patients as Young as 40 Years Old

The FDA has cleared C2N Diagnostics' PrecivityAD2 blood test for adults 40 years and older who present with signs of cognitive impairment, making it the first FDA-cleared Alzheimer disease (AD) blood test authorized for patients this young of age.¹ The clearance extends blood-based amyloid testing below the age thresholds set by the 2 previously cleared assays and adds a third option to a diagnostic category that did not exist in FDA-cleared form before 2025.

“Today’s clearance reflects how rapidly the field is advancing. Just over a year ago, there were no FDA-cleared blood tests for Alzheimer’s and now we have three,” Isobel Coleman, chief executive officer of the Alzheimer's Drug Discovery Foundation (ADDF), said in a statement.¹ "This is a proof point that sustained, early investment in translational science plays a catalytic role in moving promising ideas from the lab to patients.”

“The ADDF first invested in C2N nearly two decades ago and has stayed committed as the technology matured into a diagnostic that is now transforming how Alzheimer's is detected and diagnosed,” Coleman added in a statement.¹ “As PrecivityAD2 and tools like it move further into clinical practice, they will enable earlier detection, sharpen clinical trials, and build the foundation for precision medicine and combination therapies."

PrecivityAD2 uses high-resolution mass spectrometry to quantify plasma amyloid-beta 42/40 ratio and percent phosphorylated tau217 (p-tau217/np-tau217), combining both into a proprietary Amyloid Probability Score 2 that stratifies results into negative, positive, and an intermediate "likely positive" category. In C2N's clearance-supporting validation cohort of 1,142 symptomatic adults, the test showed a positive predictive value of 97.6% and a negative predictive value of 93.1% against amyloid PET or CSF findings; likely-positive results, occurring in 17.3% of patients, carried a 77.3% positive predictive value.

Performance was consistent across age groups and 12 chronic comorbidities, including chronic kidney disease, atrial fibrillation, and diabetes, conditions known to confound some plasma amyloid assays. The test is indicated as an adjunct to clinical evaluation in patients already undergoing workup for cognitive decline, not as a population screening tool.

READ MORE: FDA Grants Fast Track Designation to Remlifanserin for Alzheimer Disease Psychosis

AD pathology, marked by amyloid-β plaque accumulation and tau tangles, is understood to begin 15 to 20 years before clinical symptoms emerge, driving interest in biomarkers sensitive enough to flag disease processes earlier in the course of illness.² An estimated 7.4 million Americans aged 65 and older are living with AD dementia, and roughly 200,000 more under 65 have younger-onset disease, a population with limited access to biomarker confirmation since prior cleared tests were validated only in older cohorts.³ Confirming amyloid pathology has historically required PET imaging or lumbar puncture for cerebrospinal fluid (CSF) analysis, both carrying cost, access, or invasiveness barriers that slow diagnostic workup in routine neurology practice.

C2N's biomarker platform has been in development since 2008 with ADDF support, including a $7 million investment through the foundation's Diagnostics Accelerator.¹ The original PrecivityAD test, a single-analyte amyloid-beta 42/40 assay, launched in 2020 as a laboratory-developed test and was not itself FDA cleared.

C2N added the p-tau217 component and introduced PrecivityAD2 as an LDT in 2023, reporting an AUC of 0.94 against amyloid PET in a 583-patient cohort. The clearance follows the FDA's May 2025 clearance of Fujirebio's Lumipulse G pTau217/beta-amyloid 1-42 plasma ratio test for patients 55 and older, which showed 91.7% positive and 97.3% negative predictive agreement against PET or CSF in a 499-sample cohort.⁴

"PrecivityAD2 reflects how far biomarker science has come, and it points to an even bigger opportunity ahead. Tests like this don't just help to diagnose Alzheimer's, they can also identify the right patients for a clinical trial and confirm whether a drug is engaging its target,” Laura Nisenbaum, PhD, interim chief science officer at the ADDF, said in a statement.^{1 “}That kind of precision is already reshaping trial design: 83% of active Alzheimer's trials now incorporate a biomarker. As we validate the next generation of tools, we will move closer to the same transformative approach already common in cancer care: being able to match the right drugs to the right patient at the right time."

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REFERENCES
1. FDA Clearance of C2N Diagnostics' PrecivityAD2 Blood Test Advances Precision Medicine for Alzheimer's, Building on Groundwork Laid by Early ADDF Investment. News release. Alzheimer's Drug Discovery Foundation. August 20, 2026. Accessed August 21, 2026. https://www.alzdiscovery.org/news-room/announcements/fda-clearance-of-c2n-diagnostics-precivityad2-blood-test-advances-precision-medicine-for-alzheimers-building-on-groundwork-laid-by-early-addf-investment
2. Jack CR Jr, Bennett DA, Blennow K, et al. NIA-AA Research Framework: Toward a biological definition of Alzheimer's disease. Alzheimers Dement. 2018;14(4):535-562. doi:10.1016/j.jalz.2018.02.018
3. Alzheimer's Association. 2026 Alzheimer's Disease Facts and Figures. 2026. Accessed August 21, 2026. https://www.alz.org/getmedia/ef8f48f9-ad36-48ea-87f9-b74034635c1e/alzheimers-facts-and-figures.pdf
4. FDA Clears First Blood Test Used in Diagnosing Alzheimer's Disease. News release. U.S. Food and Drug Administration. May 16, 2025. Accessed August 21, 2026. https://www.fda.gov/news-events/press-announcements/fda-clears-first-blood-test-used-diagnosing-alzheimers-disease