The PrecivityAD test, offered by C2N Diagnostics, is a new blood test intended for use in patients with cognitive impairment. The test is designed to assist physicians in determining the presence or absence of amyloid plaques in the brain. PrecivityAD measures the Amyloid Beta 42/40 ratio (Aβ 42/40) and detects the Apolipoprotein E proteotype (equivalent to ApoE genotype) in blood samples. The test uses its proprietary liquid-chromatography mass spectrometry platform to measure the concentration of amyloid beta (Aβ) protein isoforms Aβ42 and Aβ40 and detect the presence of Apolipoprotein E (ApoE)-specific peptides.
The Aβ42 and Aβ40 concentrations are used to calculate the Aβ42/Aβ40 concentration ratio, which is combined with the presence or absence of an ApoE-specific peptide and the age of the patient to provide a numerical result called the Amyloid Probability Score (APS). The APS was developed using C₂N ’s proprietary algorithm, and it is used to determines the likelihood that a patient will be amyloid positive on an amyloid PET scan.
Test results are expressed as an APS algorithm score and are interpreted as follows:
A Low APS (0 to 35) is consistent with a negative amyloid PET scan result and thus indicates a low likelihood of amyloid plaques. Absence of amyloid plaques is inconsistent with an Alzheimer’s disease diagnosis and suggests other causes of cognitive symptoms should be investigated.
An Intermediate APS (36 to 57) does not distinguish between the presence or absence of amyloid plaques and indicates further diagnostic evaluation may be needed to assess the underlying cause(s) for the patient’s cognitive symptoms.
A High APS (58 to 100) is consistent with a positive amyloid PET scan result and, thus, a high likelihood of amyloid plaques. Presence of amyloid plaques is consistent with an Alzheimer’s disease diagnosis in someone who has cognitive decline, but alone is insufficient for a final diagnosis; clinical presentation and other factors should be considered along with APS.
The PrecivityAD test report gives the APS score and provides a range of Low, Intermediate and High probability of amyloid plaques.