Blood Test for Alzheimer Disease Made Clinically Available and CLIA Certified

A breakthrough in Alzheimer disease (AD) diagnosis has arrived with a blood test that measures the ratio of amyloid ß 42 to amyloid ß 40 (Aß42:Aß40) (PrecivityAD; C2N Diagnostics; St. Louis, MO) and requires only a standard blood sample. The test has been validated as being predictive of brain amyloid plaque status as determined with amyloid positron emission tomography (Aß-PET). Based on data from 686 individuals over age 60 the Aß42:Aß40 blood test correctly identified brain amyloid plaque status in 86%. The receiver operating characteristic (ROC) for the analysis had an area under the curve (AUC) of 0.88, further demonstrating the sensitivity of the test. The analysis process is automated and allows for C2N to process samples in a routine and repeatable manner.

Jeff Cummings, MD, ScD, founding director of the Cleveland Clinic Lou Ruvo Center for Brain Health and research professor, department of brain health, University of Nevada, Las Vegas, says, “Advances in Alzheimer diagnostics are key to more effective identification, diagnosis and clinical trial recruitment. A blood test for Alzheimer disease is a game changer.” Dr. Cummings is also a member of the Practical Neurology Editorial Board.

This particular Aß42:Aß40 test uses mass spectrometry and is performed in C₂N’s Clinical Laboratory Improvement Amendments (CLIA)-certified lab. CLIA regulates clinical labs to ensure accurate and reliable test results for patient specimens. Unlike PET, no radioactivity is involved. It is hoped these features will make the test more accessible than other diagnostic methods currently available for evaluating cognitive disorders.

Although this the test by itself cannot diagnose Alzheimer disease, which is still a clinical diagnosis made by a health care provider, the test provides an important tool for evaluating for the presence of Aß plaques, a key part of the amyloid tau neurdegeneration (ATN) framework advocated for diagnosis of AD. 

After analysis of a sample, the physician will receive a report detailing levels of Aß42, Aß40 and isoforms of apolipoprotein E4 as well as a composite amyloid probability score (APS) to assess the likelihood of amyloid plaques in the brain—a pathologic hallmark of AD. 

  • Low APS (0-36) is consistent with a negative amyloid PET scan and low likelihood of amyloid plaques, suggesting a diagnosis other than AD may be causing cognitive complaints
  • An intermediate APS (37-57) indicates further diagnostic evaluation may be needed to assess the underlying cause(s) for the patient's cognitive symptoms.
  • A high APS (58-100) is consistent with a positive amyloid PET scan and high likelihood of amyloid plaques, which is consistent AD in someone who has cognitive decline. 
  • Alone, no APS score is sufficient for diagnosis. It must be evaluated inthe context of the clinical presentation and other factors.

Joel B. Braunstein, MD, CEO of C₂N says, “Our mission is to translate exceptional science into unique diagnostics that can help as many people as possible. The PrecivityAD blood test introduces a new option for patients, families and the medical community that have eagerly awaited innovative tools to address Alzheimer’s troubling problems.” 

Details about a financial assistance program and payment plans are also available at

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