Types of Amyloid Tests: Blood Tests, PET, CSF, Biopsy and Microclots

Search for "amyloid test" and you'll find brain scans, spinal taps, biopsies and blood tests side by side, as if they were interchangeable. They aren't. This guide sorts the main types of amyloid tests by the question each one answers, who it's for and how it's done, so you can work out which one actually fits your situation.

Why are there so many types of amyloid tests?

Amyloid is a protein shape, not a single protein. Many different proteins can misfold into stacked, beta-sheet-rich fibrils, and each one is linked to a different condition.

Amyloid-beta builds plaques in the brain in Alzheimer's disease. Antibody light chains or transthyretin deposit in the heart, kidneys and nerves in systemic amyloidosis. Fibrin, the clotting protein, can form amyloid-like microclots in blood in research on Long COVID and inflammatory disease.

So an "amyloid test" only makes sense once you know which protein and which part of the body you're asking about. Mixing them up has real costs: a normal Alzheimer's blood test says nothing about microclots, and a microclot result says nothing about brain plaques or amyloidosis. Our pillar on the amyloid fibril test explains the lab methods that detect the amyloid shape itself. This guide is about the tests patients actually encounter.

The main types of amyloid tests at a glance

We haven't listed prices for the clinical tests. They vary widely by country, insurer and setting, and we couldn't find reliable published ranges to quote.

What is the Alzheimer's amyloid blood test?

This is the test most people mean when they search "amyloid blood test." It doesn't detect plaques directly. It measures proteins in plasma, mainly p-tau217 and the ratio of amyloid-beta 42 to 40, that track with plaque buildup in the brain.

In May 2025, the FDA cleared the first blood test to aid in diagnosing Alzheimer's disease, the Lumipulse G pTau217/β-Amyloid 1-42 Plasma Ratio. It's intended for adults aged 55 and older with signs and symptoms of the disease, in specialized care. In the FDA's review of 499 plasma samples, 91.7% of people with a positive result had amyloid plaques on PET or spinal fluid testing, and 97.3% of those with a negative result didn't. Fewer than 20% got an indeterminate result.

The science behind it built over several years. A 2020 JAMA study found plasma p-tau217 distinguished Alzheimer's dementia from other neurodegenerative diseases with an area under the curve of 0.96 in one cohort, performing about as well as spinal fluid and tau PET measures.

What the guideline says about blood tests

In 2025 the Alzheimer's Association published its first clinical practice guideline on blood-based biomarkers. It says tests with at least 90% sensitivity and 75% specificity can be used for triage, and tests with at least 90% sensitivity and 90% specificity can substitute for PET or spinal fluid testing in people with cognitive impairment seen in specialized memory care.

The panel also warned that accuracy varies a lot, that many commercial tests don't meet those thresholds, and that blood tests don't replace a full clinical evaluation. In other words, the brand and the setting both matter.

What does an amyloid PET scan show?

An amyloid PET scan uses a radioactive tracer that binds amyloid-beta plaques, then images where it collects in the brain. It's been the main reference for brain amyloid for years. The FDA notes that PET can show plaques often years before symptoms, but also that it's costly, time-consuming and involves radiation exposure.

In 2025 the Alzheimer's Association and the Society of Nuclear Medicine and Molecular Imaging updated their appropriate use criteria for amyloid and tau PET, rating 17 clinical scenarios where a scan may be considered. PET is mainly used in memory clinics, research and decisions about anti-amyloid therapies.

What do spinal fluid (CSF) amyloid tests measure?

Cerebrospinal fluid tests measure amyloid-beta and tau markers in fluid collected by lumbar puncture (a spinal tap). The FDA notes that authorized CSF tests are already in use, and that the newer blood test avoids the invasive procedure.

According to the National Institute on Aging, biomarkers like these help, but no single test can diagnose Alzheimer's or a related dementia. They're one part of a full assessment that includes history, cognitive testing and often imaging.

If you're curious about how spike protein research connects to brain amyloid, our article on spike protein amyloids cross-seeding Alzheimer's and prion proteins covers the lab studies. None of those findings are measured by the Alzheimer's tests above.

Comparing the three Alzheimer's amyloid tests

Blood tests, PET and spinal fluid testing all aim at the same target, amyloid-beta pathology in the brain, but they get there differently.

The FDA and the Alzheimer's Association both frame blood tests as part of a specialist workup in people who already have symptoms, not as a stand-alone screen.

What does a positive Alzheimer's amyloid result mean?

A positive biomarker result means amyloid pathology is likely present. It doesn't, on its own, mean someone has dementia, how fast things will change, or that amyloid is the cause of every symptom. The NIA is explicit that biomarkers are only part of a complete assessment.

False results happen too. The FDA lists false positives and false negatives as the main risks of the Lumipulse blood test: a false positive could lead to an inappropriate diagnosis and unnecessary treatment, and a false negative could delay the right care. That's why results are interpreted alongside cognitive testing and clinical history.

How is systemic amyloidosis diagnosed?

Systemic amyloidosis is a different disease family. Misfolded proteins, most often antibody light chains (AL) or transthyretin (ATTR), deposit in organs such as the heart, kidneys, liver and nerves. A 2016 Lancet seminar describes how the workup has changed, and it's built in layers:

1. Tissue biopsy with Congo red. A sample of fat, bone marrow or the affected organ is stained with Congo red and viewed under polarized light. A 2019 review cautions that Congo red alone isn't enough for diagnosis, which is why the next step matters.
2. Typing the protein. Treatment depends on which protein formed the amyloid. A 2009 Blood study showed that laser microdissection plus mass spectrometry identified the amyloid type with 100% specificity and sensitivity in a 50-case training set and 98% in a 41-case validation set. This method is now widely available.
3. Blood and urine tests. These look for a monoclonal protein, including serum free light chains, which points toward AL amyloidosis.
4. Cardiac imaging. In a multicenter Circulation study of 1,217 patients, bone scintigraphy was more than 99% sensitive and 86% specific for cardiac ATTR amyloid. When strong tracer uptake was combined with no monoclonal protein in blood or urine, specificity and positive predictive value reached 100%, allowing diagnosis without a heart biopsy in many patients.

This workup is run by hematologists, cardiologists and nephrologists. It's not something a home kit or a brain scan can replace.

What is a fibrin amyloid microclot test?

The last category is the newest and the least established. Researchers led by Resia Pretorius and Douglas Kell found that fibrin can clot into an anomalous amyloid form that resists breakdown. In their 2022 Biochemical Journal review, they describe measuring these microclots in platelet-poor plasma with Thioflavin T and a fluorescence microscope.

Our full pillar on the amyloid fibrin test covers how it works and what results show. The background research is summarized in fibrin amyloid microclots research, and the patient-facing story is in amyloid microclots and Long COVID.

The method is still evolving. In a 2023 Heliyon study, the same group said its earlier microscopy lacked objectivity and throughput, and showed that imaging flow cytometry could count and size microclots more objectively. They suggested conventional flow cytometry, already common in pathology labs, might eventually make the test easier to run.

Three caveats matter here:

• It's research-stage. There's no agreed cutoff or regulatory approval as a diagnostic test.
• It's contested. A 2024 critical appraisal by Hunt and colleagues argued the microclot hypothesis isn't supported by the evidence and that antithrombotic treatment or apheresis outside trials isn't justified. The original researchers disagree.
• It's not D-dimer. D-dimer measures fragments from clots being broken down, which is a different question. See D-dimer vs microclot test for the comparison.

Clinical next step

Looking specifically for fibrin amyloid microclots?

Our at-home amyloid fibrin test covers that one category, with a video microscopy report you can share with your doctor.

Start screening

Where our at-home kit fits

Our at-home amyloid test belongs only to this last category. It's an amyloid fibrin test: you collect a finger-prick dried blood sample at home and mail it to our partner laboratory in Mexico City. The lab stains it with Thioflavin T, the same staining principle used in the published Pretorius and Kell microclot research, and records 6K 12-bit RAW video microscopy at 20× magnification under UV illumination. Footage is reviewed with AI-assisted fibril detection plus trained human oversight.

You receive a Videographic Microscopy Report in a secure client portal, typically within 1 day of the lab receiving your sample and 5–7 business days from kit delivery including shipping. It costs $160 USD (3,200 MXN) and includes access to a directory of doctors experienced with amyloid-related care.

To be completely clear about what it isn't:

• It's not an Alzheimer's test. It doesn't measure plasma Aβ42/40 or p-tau, it isn't PET or CSF testing, and it can't detect brain amyloid plaques.
• It's not a test for systemic amyloidosis (AL or ATTR).
• It doesn't measure spike protein, D-dimer, fibrinogen or any standard coagulation value. If spike protein is your question, see spike protein persistence testing.
• It's not a diagnostic test or a medical device. It gives laboratory observational data for informational and research purposes, and a qualified healthcare provider should interpret it.

Which amyloid test should you consider?

Work backward from the question:

• Memory or thinking changes? Ask your doctor about a memory clinic referral. Blood tests, PET or spinal fluid testing may follow.
• Unexplained heart thickening, kidney protein loss, numbness or a known monoclonal protein? Ask about an amyloidosis workup with a specialist.
• Persistent fatigue, brain fog or breathlessness after COVID-19 or vaccination, with normal routine labs? That's the setting where fibrin amyloid microclot testing is being studied. Read the amyloid fibrin test guide first, and check our directory of microclot testing labs and treatment centers or our doctor directory to find clinicians familiar with the research.

Questions to bring to your appointment

Whichever path fits, these questions help you get more out of the conversation:

• Which protein and which organ is this test looking at?
• Is the test cleared or validated for someone with my symptoms and age?
• What happens next if the result is positive, negative or unclear?
• Will the result change what we do, or is it mainly for information?
• Who will interpret it, and will I get the full report?

Asking these before testing saves a lot of confusion afterward, especially with amyloid, where the same word covers such different tests.

If you want to understand the lab chemistry that ties all of these together, our amyloid fibril test guide compares Thioflavin T, Congo red, electron microscopy and seeding assays.