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Model PrecivityAD -Blood Test
The PrecivityAD® test is for individuals experiencing memory and thinking issues. The test is only available through a healthcare provider’s order.
The test is available in 49 states, the District of Columbia, and Puerto Rico; the exception is New York, which requires an individual state process for CLIA labs. C2N is working toward obtaining the requisite certifications that will permit the PrecivityAD® test to be available in New York in the near future. Please periodically refer back to this website or contact us at 1.877.C2N.DIAG (226.3424) for a status update on test availability in New York.
Healthcare Providers: If you are interested in offering the PrecivityAD® test to your patients, please complete the form to start the process for opening a test account and a C2N representative will be in touch with you shortly.
The SISAQ™ methodology is a proprietary C2N platform that enables measurement of absolute concentrations of peptides from multiple proteins in biological fluids. This mass spectrometry-based technique identifies and quantifies peptides with a high degree of specificity and precision. Multiple proteomic applications exist for this platform. By multiplexing, it is feasible to measure several biomarkers to create a multianalyte panel of plasma biomolecules (peptides, proteins, lipids, mono- and polysaccharides) that may one day help distinguish among the different classes of neurocognitive disorders. C2N’s PrecivityAD® blood test is derived from this core platform methodology.
The PrecivityAD® test uses liquid-chromatography mass spectrometry to measure the concentration of amyloid beta (Aβ) protein isoforms Aβ42 and Aβ40 and detect the presence of Apolipoprotein E (ApoE)-specific peptides in the blood. 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 Amyloid Probability Score (APS). The APS was developed using C2N ’s proprietary algorithm, and it reflects the likelihood that a patient will be amyloid positive on an amyloid PET scan.
Using data from the 686 patients, C2N Diagnostics developed an algorithm that identifies amyloid PET status based on plasma Aβ42/40 ratio, ApoE genotype, and patient age. Applying the algorithm to patient data produces an estimated Amyloid Probability Score (APS), which ranges from 0 (low likelihood) to 100 (high likelihood) that the patient will be amyloid positive on amyloid PET imaging.
FIGURE 2 (Left): Distribution of Amyloid Probability Scores (APS) grouped by amyloid PET status. (Right) Receiver operating characteristic (ROC) curve with an area under the curve of 0.88.
Figure 2 (left) depicts the APS for each of the patients in the study of 686 patients, stratified by their PET status. In this study, amyloid PET positivity was defined by a quantitative (centiloid) measurement of greater than (>) 25. The Receiver Operating Characteristic (ROC) curve (Figure 2, right) has an area under the curve (AUC) of 0.88. The algorithm’s amyloid assignment confidence increases when two cut points are defined for the test and patients with APS scores above 36 and below 58 are classified as an intermediate category. The selection of these two cut points is based on values that optimize the positive and negative predictive value of PrecivityAD® in a patient population with a 60% prevalence of amyloid PET positivity. With this population prevalence, both the positive and negative predictive value of the test is 86%, and the positive percent agreement (sensitivity) is 92% and negative percent agreement (specificity) is 77%.
Since APS reflects likelihood of the presence or absence of amyloid plaques, higher scores increase the confidence that a patient will be amyloid positive on an amyloid PET scan. Lower scores increase the confidence that a patient will be negative on an amyloid PET scan.