Clinical Information

Alzheimer disease (AD) is defined pathologically by the presence of amyloid plaques and neurofibrillary tangles in the brain. Clinical characteristics include gradual onset of mild cognitive impairment (MCI), behavioral changes such as apathy, withdrawal, or agitation, and disease progression to middle and later stage dementia.(1,2) Currently, no test detects AD with 100% accuracy; definitive diagnosis occurs at brain autopsy.

MCI impacts 12% to 18% of people in the United States over age 60 and is often an initial clinical sign of AD.(3) Detection of AD at an early stage, such as at onset of MCI or memory loss, can optimize medical management by providing access to therapies and clinical trials and by allowing for lifestyle changes that prioritize aerobic exercise, quality sleep and a healthy diet. Detection at first signs of MCI is also important for personal or family knowledge and planning, and for accessing appropriate community support and resources. Exclusion of AD with a high degree of certainty is equally important since MCI can have other etiologies, some of which are treatable.

Amyloid positron emission tomography (PET) scan and cerebrospinal fluid (CSF) testing detect brain amyloid pathology with high sensitivity and specificity in patients with MCI and early dementia.(4,5) Results of these tests are interpreted in the context of the patient’s clinical findings and other clinical work-up, as the neuropathological changes associated with AD can be seen in unaffected individuals.(4,5) Highly sensitive and specific blood biomarker testing offers an accessible and less procedurally complex option to amyloid PET scan or CSF testing for assessment of brain amyloid plaques.(6,7)

The PrecivityAD test is an analytically and clinically validated blood test that aids healthcare providers in the diagnosis of AD in patients with MCI and early-stage dementia. This evaluation simultaneously quantifies plasma amyloid beta (Abeta) 42 and 40 (Abeta42 and Abeta40) concentrations and determines the presence of apolipoprotein E (ApoE)-specific peptides (to determine APOE genotype). The test’s statistical algorithm combines the Abeta 42/40 ratio, established APOE genotype, and patient age to calculate the likelihood that a patient is positive for the presence of amyloid plaques by amyloid PET scan.(6-8) APOE proteotype/genotype, included in the test results, can aid in decision-making about treatment paths for some patients: In recent clinical trials for amyloid-reducing therapies, the E4 allele showed association with development of amyloid-related imaging abnormalities (ARIA); cerebral edema (ARIA-E); and cerebral microhemorrhages (ARIA-H).(9,10)