Alzheimer’s disease can be difficult to distinguish clinically from other causes of cognitive decline, particularly early in the illness. Confirmation of amyloid pathology may improve diagnostic confidence and is also relevant when considering amyloid-targeting treatments, but established biomarker methods such as amyloid positron emission tomography (PET) and cerebrospinal fluid (CSF) testing can be costly, invasive, or difficult to access. In August 2026, the US Food and Drug Administration (FDA) cleared C2N Diagnostics’ PrecivityAD2 blood test to aid the evaluation of adults aged 40 years and older who have signs or symptoms of cognitive impairment. It is the third FDA-cleared blood-based biomarker test for Alzheimer’s disease and the first cleared for symptomatic patients as young as 40.
PrecivityAD2 uses high-resolution mass spectrometry to measure two plasma biomarker ratios: amyloid-beta 42/40 and phosphorylated tau 217 relative to nonphosphorylated tau 217 (%p-tau217). A proprietary algorithm combines these measurements into an Amyloid Probability Score 2 (APS2), ranging from 0 to 100, which is reported in categories intended to help identify the likelihood of brain amyloid pathology associated with Alzheimer’s disease. The test may be ordered by health care professionals experienced in evaluating cognitive impairment and is intended to supplement a standard clinical assessment. It is not indicated for screening asymptomatic people and is not a stand-alone diagnostic test. C2N expects the FDA-cleared version to become available later in 2026; its current CLIA-validated laboratory test remains available in the interim.
According to the manufacturer, FDA clearance was supported by a clinical validation study of 1,142 people with signs or symptoms of cognitive decline. Test results were compared with established reference methods: amyloid PET visual interpretation or CSF biomarker testing. With dual cutoffs, a Positive result had a positive predictive value of 97.6% for brain amyloid plaques, while a Negative result had a negative predictive value of 93.1%. A Likely Positive result occurred in 17.3% of participants and had a positive predictive value of 77.3%. The manufacturer also reported that performance was consistent across the range of cognitive impairment evaluated, with increasing age, and in the presence of 12 prespecified chronic conditions, including depression, chronic kidney disease, diabetes, cardiac conditions, hypertension, obesity, and prior stroke or transient ischemic attack.
These findings suggest that PrecivityAD2 could make amyloid assessment more accessible and may reduce the need for PET or lumbar puncture in some patients. However, predictive values depend on the prevalence of amyloid pathology and the patient’s pretest probability; performance observed in a symptomatic validation population should not be extrapolated to asymptomatic screening. A positive result indicates amyloid pathology but does not by itself establish that Alzheimer’s disease is the sole cause of a patient’s symptoms. Likewise, a negative result makes amyloid pathology less likely but does not explain the cognitive impairment or exclude other neurodegenerative, medical, neurologic, psychiatric, medication-related, or substance-related causes. A Likely Positive result carries more uncertainty and should be interpreted in the context of the complete evaluation, with additional biomarker testing considered when it could change diagnosis or treatment.
For mental health clinicians, this clearance expands the diagnostic pathway for patients whose cognitive symptoms may initially present in psychiatric practice, including those with possible younger-onset disease. The test does not replace a careful history, collateral information, cognitive and functional assessment, neurologic examination, medication review, laboratory evaluation, or structural brain imaging when indicated. Clinicians should continue to assess potentially reversible contributors such as depression, sleep disorders, substance use, delirium, and medications with anticholinergic or sedating effects. Used by an experienced clinician as one component of a comprehensive workup, PrecivityAD2 may help clarify whether amyloid pathology is present and guide referral, care planning, and consideration of disease-modifying treatment.