PrecivityAD2

The recent FDA approval of anti-amyloid therapies has increased the importance of detecting Alzheimer disease at an early stage. Plasma levels of Aβ42/40 and phosphorylated tau (p-tau) appear to accurately reflect the neuropathological changes that occur in Alzheimer’s disease, including the accumulation of Aβ plaques and neurofibrillary tangles in the brain.

PrecivityAD2 is a blood-based biomarker test for Alzheimer’s disease. PrecivityAD2 simultaneously measures plasma beta amyloid and tau peptide concentrations. The ratios of amyloid β (Aβ42/40) and the percent tau that is phosporylated at threonine-217 (%p-tau217) are calculated. The results are then combined and used in a proprietary statistical algorithm to calculate an Amyloid Probability Score 2 (APS2). The score ranges from 0 to 100. A score between 0 and 47 is considered negative while a score between 48 and 100 is positive. A positive score indicates that a patient has a high likelihood of having brain amyloid plaques as determined by amyloid PET scan.

Diagnostic performance depends on a patient’s clinical stage. PrecivityAD2 has lower sensitivity and lower positive predictive value in patients with subjective cognitive decline compared to patients with mild cognitive impairment or dementia. The positive predictive value for identifying Alzheimer disease is suboptimal in people with subjective cognitive decline. Therefore, the clinical use of PrecivityAD2 should be restricted to the evaluation of patients aged 55 years and older who exhibit signs or symptoms of mild cognitive impairment or dementia.

Specimen requirement is a 10 mL purple top tube of blood. Blood must be centrifuged within 2 hours of collection and the plasma frozen at -80 degrees C. Amyloid beta and tau proteins are immunoprecipitated from plasma and then measured by liquid chromatography tandem mass spectrometry. 

PrecivityAD2 was developed by C2N Diagnostics. It has not been approved by the FDA and is not covered by insurance. 

References

Schindler  SE, Atri  A.  The role of cerebrospinal fluid and other biomarker modalities in the Alzheimer’s disease diagnostic revolution.   Nat Aging. 2023;3(5):460-462. doi:10.1038/s43587-023-00400-6.

Palmqvist  S, Tideman  P, Stomrud  E,  et al.  Blood biomarkers to detect Alzheimer disease in primary and secondary care.   JAMA. Published online July 28, 2024. doi:10.1001/jama.2024.13855.

Meyer  MR, Kirmess  KM, Eastwood  S,  et al.  Clinical validation of the precivityAD2 blood test: a mass spectrometry-based test with algorithm combining %p-tau217 and Aβ42/40 ratio to identify presence of brain amyloid.   Alzheimer's & Dementia. Published online March 16, 2024. https://alz-journals.onlinelibrary.wiley.com/doi/full/10.1002/alz.13764

Janelidze S, Barthélemy NR, Salvadó G, et al. Plasma Phosphorylated Tau 217 and Aβ42/40 to Predict Early Brain Aβ Accumulation in People Without Cognitive Impairment. JAMA Neurol. Published online July 28, 2024. doi:10.1001/jamaneurol.2024.2619.