The Alzheimer’s diagnostic pathway is changing quickly. For many years, a definitive biological workup has depended on specialist access to amyloid PET imaging or cerebrospinal fluid testing, tools that are informative, but costly, invasive, and difficult to scale. That bottleneck has become more urgent as disease-modifying therapies enter clinical practice and require earlier, more accurate identification of patients with Alzheimer’s pathology.
The FDA clearance of PrecivityAD2, a blood-based test from C2N Diagnostics built on technology developed at Washington University School of Medicine in St. Louis, adds another step toward biomarker-based dementia care. The test is cleared to aid in identifying amyloid plaques associated with Alzheimer’s disease in symptomatic patients and uses high-resolution mass spectrometry rather than an immunoassay platform.
From cognitive symptoms to molecular evidence
The clinical value of blood-based Alzheimer’s testing is not that it replaces a neurologist’s assessment. It is that it can add biological evidence earlier in the diagnostic process, before patients are sent for more invasive or less available testing.
PrecivityAD2 measures ratios involving amyloid-beta 42 and 40, as well as phosphorylated tau217 and total tau217, markers tied to amyloid pathology, one of the defining biological features of Alzheimer’s disease. Previous validation studies reported more than 90% accuracy for detecting Alzheimer’s-associated amyloid pathology, with performance comparable to cerebrospinal fluid tests and brain scans in patients with mild cognitive symptoms.
“The PrecivityAD2 test provides an accurate and reliable way to detect the presence of brain amyloid plaques associated with Alzheimer’s disease pathology based on a single blood draw,” said Randall Bateman, MD, who co-developed the underlying technology at WashU Medicine.
Why FDA clearance matters
Clinicians have already been able to order versions of the test, but FDA clearance changes the adoption landscape. It provides an added layer of regulatory review for health systems that rely on FDA-cleared diagnostics, and it may support broader payer coverage. Alzheimer’s diagnostics are no longer just about naming a syndrome; they increasingly determine whether a patient may be eligible for amyloid-targeting therapies, further confirmatory testing, or trial referral.
The Alzheimer’s Association emphasized that no blood test is currently a stand-alone Alzheimer’s diagnostic. Blood biomarkers need to be interpreted alongside clinical history, cognitive testing, neurological evaluation, imaging, and other diagnostic information.
Precision neurology becomes more scalable
Alzheimer’s disease is moving from symptom-led diagnosis toward biologically defined care. A scalable blood test could help separate patients with Alzheimer’s-associated amyloid pathology from those whose cognitive symptoms may reflect vascular disease, Lewy body disease, frontotemporal dementia, depression, medication effects, or mixed pathology.
That does not eliminate complexity. Amyloid positivity does not automatically explain every patient’s symptoms, and dementia biology is often mixed, especially in older adults. But easier access to amyloid and tau biomarker data could improve triage, reduce diagnostic delays, and help specialists focus confirmatory testing where it is most needed.
“Achieving FDA clearance of the PrecivityAD2 blood test is a key milestone in our mission to transform the diagnosis and management of Alzheimer’s disease,” said David Holtzman, MD, another WashU co-founder of C2N.
The next question is implementation. Blood-based biomarkers will have the greatest impact if they are embedded into clear care pathways: who should be tested, how results should be confirmed, when treatment decisions should follow, and how primary care and memory clinics should manage indeterminate or discordant results.
