On August 24, 2026, the Alzheimer’s Association described Roche’s Elecsys pTau217 as the fourth blood test for Alzheimer’s disease cleared by the FDA, and the second in a single week.1 News like that raises a fair question for anyone with a worried parent or a memory lapse of their own: which of these tests is which, and should I get one?

This guide compares the four tests and sets out who they are for. If you already have a result, see what a positive p-tau217 result means. For the biology behind the markers, see how Alzheimer’s blood biomarkers work.

The Short Answer

As of October 2026, the FDA has cleared four blood tests that help detect the amyloid plaques of Alzheimer’s disease: Fujirebio’s Lumipulse G pTau217/β-Amyloid 1-42 Plasma Ratio (May 2025), Roche’s Elecsys pTau181 (October 2025), and C2N’s PrecivityAD2 and Roche’s Elecsys pTau217 (both August 2026).2345 Each one is cleared for adults who already have signs or symptoms of cognitive decline, and each is meant to be read alongside a clinical evaluation, not as a diagnosis on its own.2345

They differ in who they are labeled for, where they are meant to be used and what a result can tell you. One is built mainly to rule Alzheimer’s pathology out in primary care. The other three can also point toward it. None is cleared for people without symptoms, and current guidance recommends against diagnostic testing in people whose thinking is normal, outside of research.67

Which Alzheimer’s blood tests has the FDA cleared?

All four went through the FDA’s 510(k) pathway as Class II, prescription-only devices in a category the agency calls an “Alzheimer’s disease pathology assessment test.” Each one estimates whether amyloid pathology, the plaque buildup that is one of the two defining brain changes of Alzheimer’s disease, is likely to be present.891011

The four FDA-cleared Alzheimer’s blood tests, as of October 2026
Test Maker What it measures FDA status and date Intended use Result format
Lumipulse G pTau217/β-Amyloid 1-42 Plasma Ratio Fujirebio Ratio of p-tau217 to amyloid beta 42, by automated immunoassay 510(k) clearance, May 16, 202528 Adults with signs and symptoms of cognitive decline seen in specialized care; label age 50 and older (the FDA’s announcement said 55) Two cutoffs: positive, indeterminate or negative
Elecsys pTau181 Roche, with Eli Lilly p-tau181 alone, by immunoassay 510(k) clearance, October 8, 2025; announced October 13, 202539 Adults 55 and older with signs, symptoms or complaints of cognitive decline, in primary care; not for patients already referred to a specialist One cutoff: negative or positive; built to rule out
PrecivityAD2 C2N Diagnostics Amyloid beta 42/40 ratio plus percent p-tau217, by mass spectrometry, combined into a 0–100 score (APS2) 510(k) clearance, August 19, 2026; announced August 20, 2026410 Adults 40 and older with signs or symptoms of cognitive impairment, for clinicians experienced in evaluating it Two cutoffs: positive, likely positive or negative
Elecsys pTau217 Roche, with Eli Lilly p-tau217 alone, by immunoassay 510(k) clearance, August 19, 2026; announced August 24, 2026511 Adults 55 and older with signs, symptoms or complaints of cognitive decline; same cutoffs in primary and specialty care Two cutoffs: positive, intermediate or negative

Two practical notes. C2N expects the cleared version of PrecivityAD2 to become available later in 2026; its earlier laboratory-validated version remains on offer meanwhile.4 And Lumipulse’s age limit is reported two ways: the FDA’s announcement said 55 and older, while the indications in its decision summary say 50 and older.28

Is “FDA-cleared” the same as “FDA-approved”?

No. “Cleared” means a device went through the 510(k) pathway, in which the manufacturer shows the device is “substantially equivalent” in safety and effectiveness to one already on the market. Premarket approval is a stricter route, used mainly for high-risk devices, and requires clinical trial evidence that the device is safe and effective for its intended use.12

Clearance still means something. For each test, the FDA reviewed a study comparing blood results with amyloid PET scans or spinal fluid testing, and the label spells out who the test is for and how to read each result.891011 Three things clearance does not mean:

How do Lumipulse, PrecivityAD2, Elecsys pTau217 and Elecsys pTau181 differ?

For a patient, what matters most is not the chemistry but what each result means and how often a test gives an in-between answer.

Elecsys pTau181 is a rule-out test

Elecsys pTau181 has one cutoff and was cleared to help primary care clinicians identify who probably does not have amyloid pathology. In its 312-person primary care study, where 13.1% of participants had amyloid on PET, a negative result was correct 97.9% of the time. A positive result was correct only 22.4% of the time: 132 of the 271 people without amyloid still tested positive.9 The label directs clinicians to look for other causes after a negative result and to investigate further after a positive one.9 A positive pTau181 result is a reason for referral, not an answer.

The other three tests use two cutoffs and an in-between zone

Lumipulse, PrecivityAD2 and Elecsys pTau217 each use two cutoffs. Results above the upper cutoff point toward amyloid, results below the lower cutoff point away from it, and results in between are reported as indeterminate, likely positive or intermediate.81011 The trade-off is that some people get no clear answer. In the FDA submissions, roughly one result in five landed in the middle: 19.6% for Lumipulse, 17.3% for PrecivityAD2 and 19.9% for Elecsys pTau217.81011

The middle zone means different things on different tests. On Lumipulse, 50.0% of people with an indeterminate result had amyloid. On Elecsys pTau217, 37.7% of people with an intermediate result did. PrecivityAD2’s “likely positive” category leans further, at 77.3%.81011 Each label recommends further testing or evaluation for these results.81011

How each test performed in the study the FDA reviewed (compared with amyloid PET or spinal fluid)
Test People studied Share who had amyloid Positive result: share who had amyloid Negative result: share who did not In-between results
Lumipulse 499 51.1% 91.8% 97.3% 19.6% indeterminate8
PrecivityAD2 1,142 52.7% 97.6% 93.1% 17.3% likely positive10
Elecsys pTau217 958 39.5% 88.5% 95.3% 19.9% intermediate11
Elecsys pTau181 312 13.1% 22.4% 97.9% None (single cutoff)9

Why these accuracy numbers cannot be ranked

This is not a league table. Each study enrolled a different population with a different share of people who had amyloid, and the tests handle in-between results differently.891011 Predictive values rise and fall with how common the condition is in the group tested. The Elecsys pTau217 label says so directly: a lower positive predictive value is expected in low-prevalence settings such as primary care.11

The Alzheimer’s Association’s 2025 guideline offers a brand-neutral benchmark instead. For patients with cognitive impairment seen in specialized memory care, a blood test with at least 90% sensitivity and 75% specificity can be used for triage, and one with at least 90% sensitivity and 90% specificity can substitute for amyloid PET or spinal fluid testing. The panel cautioned that many commercially available tests do not meet these thresholds, especially with a single cutoff.6

Key Point

The best test is the one validated for someone like you, in a setting like yours, read by a clinician with a plan for each possible result.

What about Alzheimer’s blood tests that are not FDA-cleared?

Some laboratories offer Alzheimer’s blood tests as lab-developed tests, which are designed, validated and run inside one certified laboratory. PrecivityAD2 itself was sold this way before its clearance.410 In 2024 the FDA issued a rule to bring lab-developed tests under its device oversight, but a federal court vacated that rule on March 31, 2025, and the FDA restored its earlier regulation in September 2025.13 In practice, a laboratory can offer an Alzheimer’s blood test that has not been through the review described above.

Some are sold directly to consumers. In July 2023, Quest Diagnostics began selling its AD-Detect amyloid beta 42/40 blood test online to adults 18 and older, with physician oversight of orders, and described it as a risk-screening test rather than a diagnostic one.14 An amyloid 42/40 ratio measures something different from the p-tau217-based tests above; see what a low amyloid beta 42/40 ratio means.

An uncleared test is not necessarily a poor one, but the FDA has not checked its claims and its numbers cannot be compared with another laboratory’s. Ask which assay it is, what population it was validated in, and whether it reports an in-between zone.

Should you get an Alzheimer’s blood test if you have no symptoms?

For most people, not yet. No FDA-cleared test is labeled for people without symptoms.2345 The 2024 Alzheimer’s Association diagnostic criteria recommend against diagnostic testing in cognitively unimpaired people and state that clinical use of these biomarkers is, for now, intended for people with symptoms.7 The 2025 blood test guideline does not extend to cognitively unimpaired people and does not address screening.6

The reason is arithmetic as much as caution. In people with normal thinking, amyloid becomes more common with age, rising from about 10% at age 50 to 44% at age 90, and APOE4 carriers have two to three times the prevalence of non-carriers.15 When a condition is uncommon in the group being tested, a larger share of positive results are false, as the pTau181 primary care data showed.9 And even a true positive in someone without symptoms describes brain biology. On its own, it cannot tell you whether or when symptoms will begin, because other brain changes and individual resilience shape that course.7

There are reasonable exceptions. Research studies test people without symptoms, with counseling built in. And some people at clearly elevated risk, such as those with two copies of APOE4 or a strong family history of early-onset disease, may decide with a specialist that a result would change concrete decisions. That is an individual judgment outside the current labels, and it works only with a plan for each possible result.

Who should and shouldn’t get an Alzheimer’s blood test?

Where an FDA-cleared Alzheimer’s blood test fits, as of October 2026
Your situation Does a cleared test fit? What to know
New memory or thinking changes, age 55 or older, being evaluated Yes, as one part of the workup A two-cutoff test can help rule amyloid in or out. The result is read with your history, examination and cognitive testing.245
Symptoms that began between 40 and 49 Only PrecivityAD2 is labeled for this age Lumipulse’s label starts at 50, and both Elecsys tests start at 55.891011
Memory concerns raised with a primary care doctor Yes: Elecsys pTau181 or Elecsys pTau217 A negative result shifts the search to other causes. A positive result calls for further evaluation, often with a specialist.911
Cognitive impairment, considering anti-amyloid treatment Yes, as part of confirming amyloid In specialty care, a test meeting the 90% sensitivity and 90% specificity benchmark can stand in for PET or spinal fluid testing.6
No symptoms, worried or curious No Outside every label; guidance recommends against diagnostic testing in people with normal cognition outside research.67
No symptoms, but APOE4 or a strong family history Not routinely Outside every label. Reasonable only after counseling with a specialist and with a plan for each possible result.
Ordering a consumer test online without your own clinician Not recommended Results arrive without the context needed to interpret them, and an in-between or false-positive result has nowhere to go.

How should you go about getting an Alzheimer’s blood test?

Inside a proper evaluation, these tests add a great deal. In a 2024 Swedish study of 1,213 patients with cognitive symptoms, a blood test based on the same mass spectrometry score that PrecivityAD2 reports (APS2) identified clinical Alzheimer’s disease with 91% accuracy, against 61% for primary care physicians and 73% for dementia specialists working without it.16 A sensible sequence:

For a parent or partner whose memory has changed, a memory evaluation with a neurologist brings these steps together so the blood test is ordered for a reason.

Common Questions

Which Alzheimer’s blood test is the most accurate?

There is no fair ranking. Each test was validated in a different population with a different share of people who had amyloid. Among the three two-cutoff tests, a positive result corresponded to amyloid in 88.5% to 97.6% of cases in their FDA studies, but 17% to 20% of people received an in-between result.81011 Fit to the patient and setting matters more than brand.

Can I order an Alzheimer’s blood test myself?

Not an FDA-cleared one. All four are prescription-only.891011 Some laboratories sell lab-developed tests directly to consumers, such as Quest’s AD-Detect amyloid 42/40 test, which Quest describes as a risk-screening test, not a diagnostic one.14 A result obtained that way still needs a clinician to interpret it.

Does a negative Alzheimer’s blood test mean I don’t have Alzheimer’s disease?

It makes amyloid pathology unlikely at the time of testing. In the FDA studies, 93.1% to 97.9% of people with a negative result had no amyloid.891011 The labels then direct clinicians to look for other causes of the symptoms.8911 Some of those causes, such as thyroid disease or low vitamin B12, are treatable. A negative result describes today. It does not guarantee the future.

Is a p-tau217 test the same as PrecivityAD2 or Lumipulse?

They overlap but are not the same. Elecsys pTau217 measures p-tau217 alone. Lumipulse divides p-tau217 by amyloid beta 42. PrecivityAD2 combines a p-tau217 ratio with the amyloid beta 42/40 ratio into one score.81011 Each has its own units and cutoffs, so a number from one cannot be compared with a number from another.

My parent has memory problems. Which test should they get?

That choice belongs to the clinician evaluating them and depends on age, setting and which test the local laboratory runs. The more important step is the evaluation itself, with a blood test used where its result would change what happens next.

The Bottom Line

Four Alzheimer’s blood tests now carry FDA clearance. All four are tools for people who already have symptoms, used inside an evaluation, and they differ in age range, setting and how they handle uncertain results.

If you have symptoms, a cleared test can shorten the path to an answer. If you do not, the honest answer for most people is to wait, work on the risk factors you can change, and revisit testing with a specialist if your situation changes. Either way, decide what you would do with the result before you have it.

Dr. Nadir Bilici, MD, DipIBLM, is a board-certified neurologist (ABPN) and Diplomate of the International Board of Lifestyle Medicine specializing in preventive neurology, Alzheimer’s prevention, and cognitive risk assessment. He sees patients by telehealth in the states where he is licensed, with in-person appointments available on a select basis.

References

  1. Alzheimer's Association. Alzheimer's Association statement on FDA clearance of Elecsys pTau217 blood test for Alzheimer's diagnosis. Press release. Published August 24, 2026. www.alz.org/news/2026/fda-clearance-elecsys-ptau217-blood-test-alzheimers
  2. U.S. Food and Drug Administration. FDA clears first blood test used in diagnosing Alzheimer's disease. Press release. Published May 16, 2025. www.fda.gov/news-events/press-announcements/fda-clears-first-blood-test-used-diagnosing-alzheimers-disease
  3. Roche Diagnostics. Roche's Elecsys pTau181 becomes the only FDA-cleared blood test for use in primary care to rule out Alzheimer's-related amyloid pathology. Press release. Published October 13, 2025. diagnostics.roche.com/us/en/news-listing/2025/fda-cleared-ptau181-alzheimers-blood-test.html
  4. C2N Diagnostics. FDA clears C2N Diagnostics' PrecivityAD2: first Alzheimer's blood test for adults with cognitive symptoms as young as 40. Press release. Published August 20, 2026. c2n.com/news-releases/bg2ziqcz39o3wxf5uc04u279ziw0yv
  5. Roche Diagnostics. Roche receives FDA clearance for Elecsys pTau217, advancing Alzheimer's disease assessment across primary and specialty care. Press release. Published August 24, 2026. diagnostics.roche.com/us/en/news-listing/2026/fda-elecsys-ptau217-alzheimers-blood-test.html
  6. Palmqvist S, Whitson HE, Allen LA, et al. Alzheimer's Association clinical practice guideline on the use of blood-based biomarkers in the diagnostic workup of suspected Alzheimer's disease within specialized care settings. Alzheimers Dement. 2025;21(7):e70535. doi:10.1002/alz.70535
  7. Jack CR Jr, Andrews JS, Beach TG, et al. Revised criteria for diagnosis and staging of Alzheimer's disease: Alzheimer's Association Workgroup. Alzheimers Dement. 2024;20(8):5143-5169. doi:10.1002/alz.13859
  8. U.S. Food and Drug Administration. 510(k) decision summary K242706: Lumipulse G pTau217/ß-Amyloid 1-42 Plasma Ratio (Fujirebio Diagnostics). Decision date May 16, 2025. www.accessdata.fda.gov/cdrh_docs/reviews/K242706.pdf
  9. U.S. Food and Drug Administration. 510(k) decision summary K252163: Elecsys Phospho-Tau (181P) Plasma (Roche Diagnostics). Decision date October 8, 2025. www.accessdata.fda.gov/cdrh_docs/reviews/K252163.pdf
  10. U.S. Food and Drug Administration. 510(k) summary K253240: PrecivityAD2 Test (C2N Diagnostics). Decision date August 19, 2026. www.accessdata.fda.gov/cdrh_docs/pdf25/K253240.pdf
  11. U.S. Food and Drug Administration. 510(k) decision summary K261686: Elecsys Phospho-Tau (217P) Plasma (Roche Diagnostics). Decision date August 19, 2026. www.accessdata.fda.gov/cdrh_docs/reviews/K261686.pdf
  12. U.S. Food and Drug Administration. Learn if a medical device has been cleared by FDA for marketing. Updated December 29, 2017. www.fda.gov/medical-devices/consumers-medical-devices/learn-if-medical-device-has-been-cleared-fda-marketing
  13. U.S. Food and Drug Administration. Laboratory developed tests. Updated September 19, 2025. www.fda.gov/medical-devices/in-vitro-diagnostics/laboratory-developed-tests
  14. Quest Diagnostics. Quest introduces first-to-market consumer-initiated blood test for Alzheimer's disease risk assessment on questhealth.com. Press release. Published July 31, 2023. newsroom.questdiagnostics.com
  15. Jansen WJ, Ossenkoppele R, Knol DL, et al. Prevalence of cerebral amyloid pathology in persons without dementia: a meta-analysis. JAMA. 2015;313(19):1924-1938. doi:10.1001/jama.2015.4668
  16. Palmqvist S, Tideman P, Mattsson-Carlgren N, et al. Blood biomarkers to detect Alzheimer disease in primary care and secondary care. JAMA. 2024;332(15):1245-1257. doi:10.1001/jama.2024.13855

Written and medically reviewed by Nadir Bilici, MD, DipIBLM. Published October 2026 · Medically reviewed on . See our editorial policy.