What are blood biomarker tests for Alzheimer's disease?

New and emerging tests detect proteins circulating in blood that are associated with Alzheimer’s disease. Tests currently available for research or clinical use detect abnormal levels of amyloid proteins in the brain, or are predictive of amyloid levels based on relative concentrations of amyloid and tau proteins. Tests for other biomarkers of Alzheimer’s disease (in blood and other fluids, and in analysis of digitally-collected data) are in active development.    

Blood biomarker testing has broad implications for Alzheimer’s disease care

Historically, treatment of Alzheimer’s disease has centered on the disabling symptoms of Alzheimer’s disease such as memory loss, cognitive impairment and dementia. Recently approved therapies target an underlying pathology of the disease by clearing abnormal concentrations of amyloid in the brain. These therapies are increasing demand for measurement of “amyloid burden” in the brain.

Conventional detection and measurement of amyloid is conducted primarily through intrusive procedures including PET (positron emission tomography) imaging, MRI (magnetic resonance imaging), or cerebrospinal fluid (CSF) analysis initiated with lumbar puncture. Blood biomarker testing offers a minimally intrusive mode of amyloid detection that could trigger redesign of care pathways for Alzheimer’s disease by creating a highly scalable and less expensive option for confirming the presence of abnormal amyloid in the brain. Potential adoption of blood biomarker testing in primary care could expedite patient access to therapy by reducing unnecessary referrals to imaging centers, neurologists, and other specialists. 

Current Landscape  

As of this writing the FDA has cleared one blood biomarker test for use in primary care, a test intended to rule out the presence of early Alzheimer’s disease. Tests intended to rule-in or rule-out Alzheimer’s disease are available as CLIA (Clinical Laboratory Improvement Act)-regulated testing services. They include tests intended for clinical use offered by diagnostic test manufacturers and by major clinical laboratory test vendors.   

Several blood biomarker tests have reached levels of accuracy on par with the accuracy of PET, CSF and MRI testing. In 2025 a clinical practice guideline on blood biomarker utilization was issued for the first time by the Alzheimer’s Association. The guideline recommends use of biomarker testing among patients with cognitive impairment, and solely within specialty care settings (neurology, geriatric psychiatry, etc.). The guideline is subject to ongoing revision that reflects an accelerating pace of published research on biomarkers of neurodegenerative disease observed since 2015.  

Challenges in adoption of blood biomarker tests

While blood biomarker tests are proving to be highly accurate, major challenges remain in determining their best and most appropriate uses.  An overarching challenge is determining how they are best integrated into the entire pathway of patient care, from a patient’s early encounters with primary care practitioners to encounters with medical specialists.

Among the challenges:

Use in specialty medicine vs. primary care:  Utilization of blood biomarker tests for Alzheimer’s disease is now in a transition phase. Biomarker testing is entering clinical practice after a period in which these tests were used only in research settings. As might be expected, initial clinical uptake of biomarker testing is concentrated among medical specialists. Further research is needed on real world implementation of biomarker testing in the primary care setting, particularly among patients with complex conditions, or with other (non-Alzheimer’s) neurological disease, and among diverse racial-ethnic populations. 

Use to rule-out, rule-in, or to confirm Alzheimer’s disease:  As noted, in 2025 the FDA approved a biomarker test for use by primary care physicians in ruling-out Alzheimer’s disease. Unresolved issues include how biomarker tests might be used to rule-in Alzheimer’s disease, at what point in the future physicians might use the tests to confirm amyloid pathology definitively, rendering a patient eligible for treatment and reducing or eliminating the need for further testing by PET, MRI, or CSF.

Use of biomarker testing vs. use of advanced cognitive assessment tools and techniques:  At present patients are evaluated for dementia, including Alzheimer’s disease, after an initial cognitive assessment ‘flags’ the patient as needing further testing. The recent Alzheimer’s Association clinical practice guideline on biomarker testing recommends their use among patients previously identified as cognitive impaired.  Meanwhile, advances in cognitive assessment are enabling prediction of Alzheimer’s disease among patients based on data from multiple modes of data collected from digital devices and other patient data sources. The relative costs and ease of adoption of blood biomarker testing and advanced cognitive assessment will determine how both technologies are best utilized in tandem.

Detection of pre-clinical Alzheimer’s disease (PCAD): Research has established that abnormal amyloid may begin to accumulate in the brain well before (even decades before) a patient experiences symptoms of Alzheimer’s disease. Clinical trials are nearing completion that may show that anti-amyloid drug therapy is effective among these ‘pre-symptomatic’ patients.[1] Blood biomarker testing may prove to be the most scalable and cost-effective means to screen asymptomatic patients for treatment should the FDA approve disease-modifying therapies for PCAD.

Physician and patient acceptance:  The advent of simple blood testing for Alzheimer’s disease presents a novel challenge for both clinicians and patients. Clinicians face the challenge of training to interpret and communicate test results to patients, and reach appropriate, compassionate shared decisions on care with patients. 

Coverage and Payment:  Coverage of conventional pathology testing for Alzheimer’s  (PET, MRI, CSF) was highly restricted before FDA approval of anti-amyloid therapies, and remains variable across payers.  As of this writing, test developers report that blood based biomarker tests are not covered by private insurance, Medicare, or Medicaid. Patients are responsible for paying for testing out-of-pocket, and cost represents a barrier to equitable access to testing.