Nelson Vergel
Founder, ExcelMale.com
Until May 2025, confirming amyloid plaques in a living person meant a PET scan or a spinal tap. Both are accurate, both are expensive, and one involves a needle in your lower back. In roughly 15 months, the FDA cleared four blood tests that read the same underlying biology from a standard blood draw. That is a fast shift for a field that spent decades unable to see these plaques outside of an autopsy.
What FDA-cleared blood tests can detect Alzheimer's-related amyloid pathology?
Four tests currently hold FDA clearance: Lumipulse G, Elecsys pTau181, PrecivityAD2, and Elecsys pTau217. Each measures proteins in blood plasma that track with amyloid plaque buildup in the brain, the hallmark change of Alzheimer's disease. Here is what each one is and what it measures.
Lumipulse G pTau217/beta-Amyloid 1-42 Plasma Ratio (Fujirebio)
Cleared May 16, 2025, Lumipulse G was the first blood test the FDA authorized to aid Alzheimer's diagnosis. It measures two proteins, pTau217 and beta-amyloid 1-42, and calculates the ratio between them. That ratio correlates with the presence or absence of amyloid plaques. In the pivotal 499-sample study, 91.7% of people with a positive result had amyloid confirmed by PET or spinal fluid, and 97.3% of those with a negative result were confirmed amyloid-negative (Fujirebio, 2025). It is indicated for symptomatic adults 55 and older, typically in specialized care.
Elecsys pTau181 (Roche, with Eli Lilly)
Cleared October 13, 2025, Elecsys pTau181 is the only FDA-cleared blood test indicated for use in primary care specifically to rule out Alzheimer's-related amyloid pathology. It measures a single protein, phosphorylated tau 181. A negative result means Alzheimer's pathology is unlikely, which lets a primary care clinician avoid an unnecessary specialist referral. Roche reported a 97.9% negative predictive value in a low-prevalence population reflective of primary care (Roche, 2025). It is intended for adults 55 and older with signs, symptoms, or complaints of cognitive decline.
PrecivityAD2 (C2N Diagnostics)
Cleared August 20, 2026, PrecivityAD2 is the first FDA-cleared Alzheimer's blood test for symptomatic adults as young as 40. It uses high-resolution mass spectrometry to measure the Abeta42/40 ratio and the p-tau217/np-tau217 ratio (%p-tau217), then combines them into a proprietary Amyloid Probability Score 2 (APS2) that runs from 0 to 100. In a 1,142-participant validation study, a positive result carried a 97.6% positive predictive value and a negative result a 93.1% negative predictive value against PET or spinal fluid (C2N Diagnostics, 2026). Its performance held steady across 12 chronic conditions common with aging, including kidney disease and diabetes.
Elecsys Phospho-Tau (217P) Plasma (Roche, with Eli Lilly)
Cleared August 24, 2026, Elecsys pTau217 is the first and only FDA-cleared single-biomarker blood test that supports both rule-in and rule-out of amyloid pathology using the same clinical cutoffs across primary and specialty care. It measures phosphorylated tau 217. Roche reported roughly 92.5% negative predictive value and 96.6% positive predictive value against PET (Roche, 2026). It is intended for adults 55 and older with signs, symptoms, or complaints of cognitive decline.
How do these four Alzheimer's blood tests differ from each other?
They differ on four things that matter clinically: what protein they measure, the youngest age they cover, whether they are built to rule Alzheimer's in or out, and which care setting they are meant for. The table below lays out each side by side.
| Feature | Lumipulse G | Elecsys pTau181 | PrecivityAD2 | Elecsys pTau217 |
|---|---|---|---|---|
| Maker | Fujirebio | Roche + Lilly | C2N Diagnostics | Roche + Lilly |
| FDA cleared | May 16, 2025 | Oct 13, 2025 | Aug 20, 2026 | Aug 24, 2026 |
| Biomarker | pTau217/Abeta 1-42 ratio | pTau181 (single) | Abeta42/40 + %p-tau217 (APS2) | pTau217 (single) |
| Age indicated | 55 and older | 55 and older | 40 and older | 55 and older |
| Primary use | Rule in | Rule out | Rule in + rule out | Rule in + rule out |
| Care setting | Specialty | Primary care | Experienced cognitive care | Primary + specialty |
| Result type | Ratio (continuous) | Positive / negative | APS2 score 0-100 | Positive / negative |
| Reported PPV | 91.7%* | Not the focus | 97.6% | 96.6% |
| Reported NPV | 97.3%* | 97.9% | 93.1% | 92.5% |
*Lumipulse figures are reported as percent agreement with PET or CSF rather than PPV/NPV in a defined-prevalence sample. Predictive values shift with the underlying prevalence of amyloid in the population tested, so numbers are not perfectly head-to-head across studies.
Which test fits which patient and care setting?
It depends on the patient's age, where they are being seen, and whether the goal is to rule Alzheimer's in or out. The four tests were designed for different points in the diagnostic path, so they are more complementary than competing.
A primary care doctor seeing an older patient with early memory complaints is the target user for Elecsys pTau181 or Elecsys pTau217. A negative pTau181 result rules Alzheimer's out and spares a referral. pTau217 can do both rule-in and rule-out in that same primary care visit.
A younger patient, someone in their 40s or early 50s with cognitive symptoms, is where PrecivityAD2 stands apart, since it is the only one of the four cleared below age 55.
A memory clinic or neurologist confirming amyloid before considering an amyloid-targeting drug such as lecanemab or donanemab may reach for Lumipulse G, PrecivityAD2, or pTau217, all of which are geared toward ruling amyloid in. Which one a clinic uses often comes down to the analyzer already installed in its lab.
How accurate are these blood tests compared to PET scans and spinal taps?
They are accurate enough that the FDA cleared them against PET and spinal fluid as the reference standard, but they are aids, not replacements. Each was validated by comparing its result to amyloid PET imaging or cerebrospinal fluid biomarkers, which remain the confirmatory tests.
The negative predictive values are the strongest numbers here. A 97.9% NPV for pTau181 means that out of 100 people it calls negative, roughly 98 truly do not have amyloid pathology. That is why the rule-out framing matters: these tests are very good at telling you when Alzheimer's is unlikely.
Positive results carry more caveats. Lumipulse G left under 20% of its samples in an indeterminate zone that resolved to neither positive nor negative (NeurologyLive, 2025). A positive blood result is a signal to confirm, not a diagnosis on its own.
What can these blood tests not tell you?
They cannot tell you that you will get Alzheimer's, and they are not meant for people without symptoms. Every one of the four is cleared only as an aid in evaluating adults who already have cognitive symptoms, used alongside clinical judgment.
They detect amyloid pathology, which is one feature of Alzheimer's, not the whole disease. Amyloid can be present in people who never develop dementia, and cognitive decline can have causes that have nothing to do with amyloid. A positive result does not name the cause of a person's symptoms by itself.
They are also not population screening tools. The manufacturers and the FDA are explicit that these tests are for symptomatic evaluation, not for checking healthy people out of worry. Test performance is measured in symptomatic populations, and running them on people without symptoms produces far more false positives than the reported numbers suggest.
One honest limit worth stating: most validation to date has been done in populations that are not fully representative of everyone who will be tested. Performance across racial, ethnic, and socioeconomic groups is still being studied, and this is an area where the data are not yet complete.
Frequently Asked Questions
Can I get an Alzheimer's blood test if I have no symptoms?
No. All four FDA-cleared tests are indicated only for adults who already have signs, symptoms, or complaints of cognitive decline. They are not approved for screening people without symptoms.
Do these blood tests replace a PET scan or spinal tap?
Not entirely. They reduce the need for PET and spinal fluid testing, and a negative result can make those unnecessary. A positive blood result is often confirmed with PET or CSF before a diagnosis is made.
Which test can be used in a regular doctor's office?
Elecsys pTau181 and Elecsys pTau217 are both cleared for primary care. pTau181 is built to rule Alzheimer's out; pTau217 can rule it in or out in the same setting.
What is the youngest age these tests cover?
PrecivityAD2 is cleared for symptomatic adults as young as 40. The other three are indicated for adults 55 and older.
What does an APS2 score mean on the PrecivityAD2 test?
APS2 is a number from 0 to 100 that estimates the likelihood that amyloid pathology is present. It combines the Abeta42/40 ratio and %p-tau217 into one score. A higher number means a higher probability of amyloid.
The Bottom Line
Here is the practical point the marketing around these launches tends to skip: the real value of a blood test this good is often the negative result. If you or a family member has early memory concerns, a negative pTau181 or pTau217 can close the door on Alzheimer's and push the workup toward treatable causes, from thyroid problems to sleep apnea to medication side effects. That is a faster, cheaper answer than the old path, and for a lot of families it is the answer they actually needed.
If cognitive health is on your radar, it is worth understanding how hormones, metabolic health, and sleep intersect with brain aging. See our related coverage on (testosterone and cognitive function) and (metabolic health in men over 50).
Related ExcelMale Forum Discussions
[Nelson: add relevant ExcelMale thread URLs here, one line each. No cognitive-health threads were provided for this build.]
Key References
- Hu Y, et al. The pTau217/Abeta1-42 plasma ratio: the first FDA-cleared blood biomarker test for diagnosis of Alzheimer's disease. PubMed, 2025. https://pubmed.ncbi.nlm.nih.gov/40582836/
- Fujirebio. Fujirebio receives marketing clearance for Lumipulse G pTau217/beta-Amyloid 1-42 Plasma Ratio. Press release, 2025. https://www.fujirebio.com/en-us/news-events/fujirebio-receives-marketing-clearance
- Roche. Elecsys pTau181 becomes the only FDA-cleared blood test for use in primary care to rule out Alzheimer's-related amyloid pathology. Investor update, 2025. Roche’s Elecsys® pTau181 becomes the only FDA-cleared blood test for use in primary care to rule out Alzheimer’s-related amyloid pathology
- Roche. Roche receives FDA clearance for Elecsys pTau217, advancing Alzheimer's disease assessment across primary and specialty care. Press release, 2026. https://diagnostics.roche.com/us/en/news-listing/2026/fda-elecsys-ptau217
- C2N Diagnostics. FDA clears C2N Diagnostics' PrecivityAD2, first Alzheimer's blood test for adults with cognitive symptoms as young as 40. Press release, 2026. https://precivityad.com/news/fda-clears-precivityad2
- Alzheimer's Association. Welcomes FDA clearance of first blood test for use in primary care to rule out Alzheimer's-related amyloid pathology. News, 2025. https://www.alz.org/news/2025/fda-clearance-blood-test-primary-care
- Mayo Clinic. New FDA-approved blood tests for diagnosing Alzheimer's disease. Patient information, 2025. https://www.mayoclinic.org/diseases-conditions/alzheimers-disease/in-depth/new-blood-tests-alzheimers
- Practical Neurology. Blood-based p-tau181 testing for Alzheimer's pathology now cleared by the FDA for the primary care setting. News, 2025. https://practicalneurology.com/news/blood-based-p-tau181-testing
