New research finds that C₂N Diagnostics proprietary algorithm used in its PrecivityAD2 blood test, which is used by healthcare providers to determine Alzheimer’s disease (AD) pathology in individuals with early cognitive impairment, can identify brain amyloid status with “sensitivity, specificity, positive and negative predictive values that approximate those of amyloid positron emission tomography (PET) imaging.”

C₂N Diagnostics believes the findings in “Alzheimer’s & Dementia: The Journal of the Alzheimer’s Association” are significant as the healthcare sector needs a PET scan alternative that’s widely accessible, accurate, and cost-effective that can aid in the differential diagnosis of AD and AD-related dementias, the company says.

The AUC-ROC for the PrecivityAD2 test output, the Amyloid Probability Score 2 (APS2), was 0.94, yielding 88% agreement with brain amyloid status based on a single cut-off value. Diagnostic performance of the APS2 was similar by ethnicity, sex, age, and apoE4 status. The APS2 result was the most robust method among the individual plasma amyloid and tau analytes measured to identify disease.

The research findings also showed that the AUC-ROC for the %p-tau217 (0.94), one of the core components of the APS2 algorithm, was superior to that for the p-tau217 concentration (0.91) for identifying brain amyloidosis. The researchers define %p-tau217 as the percentage of p-tau217 relative to np-tau217. These data showing the superiority of %p-tau217 over p-tau217 alone reaffirm the findings of another study recently published involving C2N’s technology to identify amyloid pathology in pre-clinical AD with high accuracy comparable to amyloid PET.

PrecivityAD2 Blood Test Study

In the published study, the PrecivityAD2 blood test was clinically validated in 583 individuals with cognitive impairment across two independent cohorts. The robustness of the findings was enhanced by the fact that one of the study cohorts, PARIS, included a prospective, difficult-to-diagnose, real-world population of U.S. Medicare beneficiaries presenting with memory concerns to clinics as part of a substudy of IDEAS(1).

The PrecivityAD2 blood test determines a patient’s likelihood (positive or negative) for the presence of amyloid plaques in the brain, one of the brain pathology findings of Alzheimer’s disease. In addition to helping healthcare providers determine Alzheimer’s disease pathology, the PrecivityAD2 test aids in medical management and treatment decisions.

“This latest research adds to the growing body of data that affirms the PrecivityAD2 test’s outstanding diagnostic performance and builds further confidence in the healthcare sector,” says Joel Braunstein, MD, MBA, C₂N’s CEO. “The PrecivityAD2 blood test provides a less costly, more accessible and vitally needed option for healthcare providers who must conduct diagnostic testing for their patients facing memory and dementia care issues. We’re excited that additional studies are underway throughout the world that are seeking to further demonstrate the robust clinical performance and generalizability of the APS2 model.”

Further reading: Blood Biomarkers in C2N Test Accurately Evaluate Brain Amyloid in Preclinical Alzheimer’s

Braunstein and others note the PrecivityAD2 test’s appeal because of PET’s limitations for screening large number of patients as new disease-modifying drugs that can specifically treat the underlying causes of AD become available. These limitations include: PET’s cost for research use (currently estimated at around $6,500); that it exposes patients to radiation; and that it’s not easily accessible outside of large cities.

The PrecivityAD2 blood test is intended for use in patients aged 55 and older with signs or symptoms of mild cognitive impairment or dementia who are undergoing evaluation of Alzheimer’s disease or dementia. Only a healthcare provider can order the PrecivityAD2 test.

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 certification that will permit the PrecivityAD2 test to be available in New York in the near future.


  1.; Identifier: NCT02420756.