Screening, Detection and Diagnosis of Alzheimer's Disease

What are Alzheimer's blood tests?

Despite the growing scale of the crisis, Alzheimer’s disease remains significantly underdiagnosed. Blood tests offer a faster, less invasive and potentially more accessible way to detect biological signs of Alzheimer’s.

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Why early detection matters

Fewer than 10% of people with Alzheimer’s are diagnosed during the mild cognitive impairment (MCI) stage, when symptoms may still be subtle and current disease-modifying treatments can be an option. (1)

In the past, confirming a diagnosis of Alzheimer’s disease has been complicated, time-consuming, expensive, and relied on invasive testing. (1) Now, blood-based biological markers (biomarkers) — measurable signs in the body — can help check for biological signs of Alzheimer’s disease. Since the FDA cleared the first Alzheimer’s blood test in May 2025, four tests have received FDA clearance. (2)

Why are blood tests such an important innovation in early detection?

Earlier diagnosis can create more opportunity to slow disease progression and preserve cognitive function for longer—giving people and their families more time to plan, make decisions and maintain quality of life. (3)

Today, confirming an Alzheimer’s diagnosis can involve multiple assessments, expensive positron emission tomography (PET) imaging, or invasive cerebrospinal fluid (CSF) testing. Access to specialists and advanced testing is also limited. On average, dementia broadly takes approximately three and a half years to diagnose after symptoms begin. (4,5)

Blood tests could make testing faster and more accessible, particularly in primary care, where many people first seek help for memory or other cognitive concerns. This could broaden the reach of earlier detection, particularly for populations that face disparities in Alzheimer’s diagnosis and access to specialty care.

These tests can also be highly accurate. Studies have found that some blood-based biomarker tests can identify Alzheimer’s-related changes with approximately 90% accuracy, compared with 73% among specialists in memory clinics and 61% among primary care physicians using standard clinical evaluations. (6)

With results available in as little as a few days, blood tests could mean a shorter path from concern to answers and, when appropriate, treatment. (2)

What are the latest Alzheimer’s biomarker tests?

The Alzheimer’s testing landscape has shifted rapidly with the introduction of blood-based biomarkers into clinical care. These tests measure biomarkers in different ways, but all are designed to help determine whether Alzheimer’s-related amyloid changes are likely to be present.

Test	Company	Biomarkers measured	FDA clearance date	Key things to know
Elecsys Phospho-Tau (217P) Plasma	Roche	p-tau217	August 19, 2026	Measures p-tau217 alone using established clinical cutoffs.
PrecivityAD2	C2N Diagnostics	p-tau217 + amyloid beta 42/40	August 19, 2026	Combines amyloid beta and p-tau217 using a proprietary algorithm to assess the likelihood of Alzheimer’s-related changes.
Elecsys Phospho-Tau (181P) Plasma	Roche	p-tau181	October 8, 2025	Measures p-tau181 alone using established clinical cutoffs.
Lumipulse G pTau217/β-Amyloid 1-42 Plasma Ratio*	Fujirebio	p-tau217 + amyloid beta 42	May 16, 2025	Combines p-tau217 and amyloid beta to assess the likelihood of Alzheimer’s-related changes.

* Fujirebio has recalled certain Lumipulse test materials because they could produce inaccurate results.

(7) https://www.alz.org/getmedia/ef8f48f9-ad36-48ea-87f9-b74034635c1e/alzheimers-facts-and-figures.pdf
(8) https://www.medicalnewstoday.com/articles/fda-clears-first-single-biomarker-blood-test-alzheimers-4-experts

How do Alzheimer’s blood tests work?

Alzheimer’s blood tests measure biomarkers—measurable signs in the body, that can provide information about what is happening in the brain; much like cholesterol is a biomarker of cardiovascular health. They focus primarily on amyloid beta and tau, proteins that build up abnormally in the brain and form the hallmark plaques (amyloid) and tangles (tau) of Alzheimer’s. (1) Unlike genetic testing, which looks for signs that may increase a person’s risk, biomarkers look for biological changes associated with the disease.

Biomarker	What it is	What to know
Amyloid beta	A protein that can build up in the brain as abnormal amyloid plaques.	Builds up as amyloid plaques.
Tau	A protein found inside brain cells that can become abnormal and form tau tangles.	Can form tau tangles.
p-tau217	A specific form of tau that can be measured in the blood and is especially useful for detecting Alzheimer's-related amyloid changes.	Research shows p-tau217 can accurately indicate whether Alzheimer’s-related amyloid changes are present in the brain, with some studies showing about 90% agreement with amyloid PET results.¹

(1)https://www.alz.org/getmedia/ef8f48f9-ad36-48ea-87f9-b74034635c1e/alzheimers-facts-and-figures.pdf
(6) https://jamanetwork.com/journals/jama/fullarticle/2821669

Who should get an Alzheimer’s blood test?

FDA-cleared Alzheimer’s blood tests are for adults who are experiencing signs or symptoms of cognitive decline.
Age requirements vary by test and generally begin at age 50 or 55.
They are not currently intended as routine screening for people without cognitive symptoms. (9)

If you are unsure what changes mean or what to do next, the BrainGuide questionnaire can help you explore your concerns and connect with relevant resources for next steps.

What do my test results mean?

The way results are reported and interpreted varies by test, but some test results are either positive, negative or intermediate.

If I get a positive result, does that mean I have Alzheimer’s disease?
A positive result means Alzheimer’s-related changes are likely to be present in the brain. However, a positive blood test alone does not necessarily mean that Alzheimer’s disease is the cause of your symptoms. Your health care provider will interpret the result alongside your symptoms, medical history, cognitive assessment and other clinical information to determine a diagnosis and appropriate next steps. (9)

What does a negative result mean?
A negative result means Alzheimer’s-related changes are less likely to be present. It does not explain what is causing those symptoms, so further evaluation may still be needed. (2)

What does an intermediate result mean?
An intermediate result means it is unclear whether Alzheimer’s-related changes are present. In these cases, additional testing with amyloid PET imaging or CSF testing may be needed to clarify the result. (2)

Can other health conditions affect my results?
Yes, certain health conditions can affect Alzheimer’s blood biomarker levels. Kidney disease, for example, can raise blood levels of p-tau217 and lead to a false positive for Alzheimer's-related changes. (10)

What can’t these tests tell me?
Alzheimer’s blood tests do not provide a complete explanation for possible cognitive changes or distinguish among all possible causes of dementia. Memory and thinking changes can be related to Alzheimer’s disease, other neurodegenerative diseases, vascular changes, medications and other medical conditions. (5) Other tests, including cognitive assessments, laboratory testing and brain imaging, may still be needed to understand what is causing a person’s symptoms.

How can I access a test?

FDA-cleared Alzheimer’s blood tests are ordered by a health care provider and are increasingly available through primary and specialty care. If testing is not available through your primary care provider, ask for a referral to a specialist.

Important Note: Other Alzheimer’s blood tests are available commercially, including directly to consumers. These tests have not undergone the same FDA review and may not include clinical guidance to help you understand your results and next steps.

What will a test cost?

The cost of Alzheimer’s blood testing varies by test, laboratory and insurance coverage, but blood tests are expected to be less expensive than PET imaging or CSF testing. Check with your health care provider or insurance plan about the specific test being ordered. (9)

Medicare coverage is also evolving. The bipartisan Alzheimer’s Screening and Prevention (ASAP) Act has been introduced in Congress to expand Medicare coverage of FDA-cleared blood-based screening tests for Alzheimer’s and related dementias. (11)

Where are Alzheimer’s blood tests headed next?

Can blood tests replace PET imaging or lumbar punctures?
For some patients, they already are. Highly accurate blood biomarker tests can be used in place of PET imaging or CSF testing in certain situations, reducing the need for more invasive, expensive or less accessible testing. (1)

Could blood tests eventually become part of routine screening?
For people experiencing cognitive concerns, broader availability and insurance coverage could lead to earlier, more accurate diagnosis, when more treatment options may be available. (1)

Looking further ahead, researchers are studying whether biomarkers such as p-tau217 could help identify people at risk before symptoms appear. Today’s FDA-cleared tests are not intended for routine screening of people without symptoms, but future tests could potentially become part of preventive care. (12)

Could blood biomarkers eventually help monitor disease progression or response to treatment?
Clinical trials are already exploring this possibility. Roche’s Phase III PrevenTRON trial of trontinemab is using the Elecsys pTau217 blood test alongside PET imaging to help identify participants and track changes during treatment. (13)

Special Thanks

Thank you to Genentech for their generous support for our efforts to provide timely and relevant education around the latest Alzheimer's diagnostic innovations.

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