FDA Clears Novel Alzheimer's Blood Test

 The FDA cleared the PrecivityAD2 blood test to help diagnose Alzheimer's disease as part of a standard clinical workup, C2N Diagnostics announced Thursday.

The test, which measures plasma amyloid beta and tau peptide ratios to assess the likelihood of brain amyloid plaques, is the first Alzheimer's blood-based biomarker for people as young as 40 with cognitive symptoms.

PrecivityAD2 is indicated for adults with signs or symptoms of cognitive impairment being evaluated for Alzheimer's or other forms of cognitive decline. It's intended to be used with a clinical assessment to help healthcare professionals identify patients with amyloid pathology, not as a screening or standalone diagnostic test.

The test uses high-resolution mass spectrometry to quantify Alzheimer's disease biomarkers in blood, producing an outcome called the amyloid probability score 2 (APS2). The APS2 incorporates the ratio of plasma phosphorylated tau 217 (p-tau217) relative to non-p-tau217, combined with a plasma amyloid-beta 42/40 ratio, to rule in or rule out Alzheimer's disease.

In a validation study of 1,142 people with signs or symptoms of cognitive decline, PrecivityAD2 showed a 97.6% positive predictive value (rule-in) and a 93.1% negative predictive value (rule-out) to detect brain amyloid plaques using dual cutoffs measured against amyloid PET or cerebrospinal fluid testing, C2N reported. The test was effective at detecting plaques in a wide range of patients, including people with mild symptoms and those with more advanced cognitive impairment.

PrecivityAD2 showed consistent diagnostic performance as age increased and in people with comorbidities like atrial fibrillation, autoimmune or inflammatory disease, chronic heart failure or kidney disease, coronary heart disease, depression, diabetes, dyslipidemia, history of cancer, history of stroke or transient ischemic attack, hypertension, or obesity, the company added.

A recent study in Sweden showed the test was useful to help primary care physicians rule out Alzheimer's disease. Earlier research showed the APS2 score performed better than primary care doctors or dementia specialists in detecting Alzheimer's disease among people with cognitive symptoms.

In 2025, the FDA cleared two other diagnostic blood tests for Alzheimer's disease: one to help clinicians identify Alzheimer's in people with signs and symptoms, the other to rule out Alzheimer's disease in primary care.

Lab-developed tests not approved by the FDA are also on the market. Last year, the Alzheimer's Association issued guidance outlining sensitivity and specificity parameters for Alzheimer's blood tests to either triage or diagnose people with cognitive impairment.

An estimated 19 to 20 million U.S. adults 65 and older, and hundreds of thousands more between the ages of 45 and 65, have cognitive impairment and may benefit from an early diagnosis, C2N Diagnostics noted.

PrecivityAD2 can be ordered by healthcare professionals experienced in evaluating patients with cognitive impairment, the company stated. It currently is available as a lab-developed test; the FDA-cleared test version is expected to be available later this year.

https://www.medpagetoday.com/neurology/alzheimersdisease/122701