Two approvals ten days apart changed what a memory clinic can offer in 2026: the FDA approved TAUKLARIFY, a second tau PET imaging agent, on August 14, and cleared Roche's Elecsys pTau217 blood test on August 24. For most patients, the blood test is the one that will reach them first — Lantheus has not announced a general commercial launch for TAUKLARIFY, while a blood draw runs on analyzers that hospitals already own.
Tau and amyloid are the two proteins that define Alzheimer's disease under current diagnostic criteria. The new blood test looks for amyloid pathology; the new scan looks for tau neurofibrillary tangles, the twisted protein filaments inside neurons that track most closely with symptoms. Knowing which test answers which question is the practical difference between an informed appointment and a confusing one.
Medical information disclaimer: This article is for general educational purposes only and does not provide medical advice, diagnosis, or treatment. Always consult a physician or other qualified health professional about symptoms, medications, tests, or treatment decisions.
Table of Contents
- What TAUKLARIFY Is and What It Detects
- The Blood Test That Arrived Ten Days Later
- Which Test Answers Which Question
- The Limits Printed on the Label
- Why the Scan May Not Be Available Where You Live
- What Comes Next in Blood-Based Staging
- Frequently Asked Questions
What TAUKLARIFY Is and What It Detects
TAUKLARIFY (florquinitau F 18, previously known in research as MK-6240) is an injected radioactive tracer that binds to tau tangles so a PET scanner can photograph them. According to Lantheus's approval announcement, the FDA approved it for brain imaging to identify tau neurofibrillary tangle pathology in adults with cognitive impairment being evaluated for Alzheimer's disease. It is the second approved tau tracer, following Tauvid in 2020. The evidence behind the approval came from two blinded-read studies of images from more than 500 subjects across three trials.
Those trials spanned mild cognitive impairment, mild Alzheimer's dementia, and people with no cognitive symptoms at all — which matters, because a tracer has to distinguish disease from normal aging, not just confirm what is already obvious. Safety data came from 1,734 subjects. The most common reactions were headache in 0.7% and nausea in 0.2%, and the prescribing information lists no contraindications. For a patient weighing the scan, the physical burden is an IV injection, a radiation dose, and time on a scanner table — not a meaningful side-effect risk.
The Blood Test That Arrived Ten Days Later
On August 24, 2026, the FDA cleared Roche's Elecsys pTau217 plasma immunoassay through the 510(k) pathway as K261686. The test was co-developed with Eli Lilly and cleared for adults aged 55 and older who have symptoms of cognitive decline. Roche describes it as the first FDA-cleared single-biomarker blood test that supports both ruling in and ruling out amyloid pathology using the same cutoffs in primary care and specialty care. That last detail is the quiet headline.
One set of thresholds that works in a family doctor's office means a primary care physician can order the test without a memory-clinic referral first, and the result means the same thing it would mean downstream. The labeling returns three results, not two: positive, intermediate, and negative. Roche's diagnostics announcement states the test is not a standalone diagnostic and must be read alongside other clinical information. An intermediate result does not end the workup — it routes the patient onward to PET imaging or a cerebrospinal fluid test.
Which Test Answers Which Question
These two tools are not competitors for the same decision. They sit at different points in the same pathway, and ordering them in the wrong order wastes money and time. The Alzheimer's Association published its first blood-biomarker clinical practice guideline in July 2025, peer-reviewed that December.
Its guidance permits a test with at least 90% sensitivity and 75% specificity to be used for triage, and requires at least 90% on both measures before a blood test can replace amyloid PET or CSF testing. The guideline also warns that many commercially available tests fall short of those thresholds. One rule in that guideline applies to every reader: no blood biomarker test should be ordered before a comprehensive clinical evaluation. A biomarker result without a cognitive assessment, a medication review, and a history is a number without a question attached to it.
- **Elecsys pTau217 (blood):** asks whether amyloid pathology is likely present. Best used early, after a clinical evaluation, to decide whether specialist testing is warranted at all.
- **TAUKLARIFY (PET):** asks whether tau tangles are present and where. Best used later, in a specialist setting, when amyloid status is already known and the question is disease stage or confirmation.
- **Intermediate blood result:** the specific trigger for escalating to PET or CSF, per the Roche labeling.
- **Neither test alone:** sufficient to diagnose Alzheimer's disease. Both labels are explicit that results are interpreted alongside the clinical picture.
The Limits Printed on the Label
TAUKLARIFY's own label sets boundaries that a patient should hear before the scan, not after. As Practical Neurology reported on the approval, safety and effectiveness are not established for non-Alzheimer's tauopathies — the other diseases, such as progressive supranuclear palsy, that also involve tau. The label further states that a positive or negative scan does not independently confirm or exclude tau pathology. The sharpest limitation concerns exactly the patients most likely to seek the scan. Performance may be lower in people at earlier stages of the pathologic spectrum.
In plain terms: someone with early mild cognitive impairment can scan negative and still have the disease. A clean image at that stage is reassuring, not conclusive, and it does not retire the question. Blood testing has its own reliability problem, and it is batch-specific rather than conceptual. The FDA device recall database records that Fujirebio initiated a Class 2 recall, Z-1302-2026, of specified Lumipulse G pTau217/β-Amyloid 1-42 Plasma Ratio lots on December 11, 2025, posted February 5, 2026. Customers were told to immediately discontinue the listed lots because of a higher frequency of indeterminate and positive classifications — meaning some patients were told their result was abnormal or unclear when a different lot might have said otherwise.
Why the Scan May Not Be Available Where You Live
Approval and availability are separate events. Lantheus said that after approval it intends to continue supporting Alzheimer's therapeutic programs through its Pharma Solutions business while assessing the appropriate path toward broader commercial availability. No general launch date accompanied the approval. In practice, that means most memory clinics could not order a TAUKLARIFY scan on announcement day.
Radiopharmaceuticals with an 18-fluorine label decay within hours, so they must be produced at a regional cyclotron and shipped same-day. Distribution has to be built network by network, and clinical trial sites typically get access before community practices. If a neurologist mentions tau PET, the useful follow-up questions are concrete: which tracer the site stocks, whether Tauvid is available instead, and whether the result would change the treatment plan. A scan that confirms something already decided is a radiation dose and a bill without a corresponding decision.
What Comes Next in Blood-Based Staging
The research frontier is no longer detection — it is staging, meaning how far the disease has progressed. A two-step blood strategy from Lund University and Washington University, published in Lancet Neurology and summarized by Practical Neurology, runs p-tau217 first and then a second marker, eMTBR-tau243, only in those who test positive. Among p-tau217-positive participants, the sequence identified established Alzheimer's disease with 81% accuracy.
It identified high tau burden with 87% accuracy and a 90% negative predictive value — so a negative second-step result reliably indicated that heavy tau pathology was not present. Those are research-assay numbers. eMTBR-tau243 has no FDA clearance for staging, and no clinic can order it as a clinical test today. For now, tau staging still means imaging, which keeps TAUKLARIFY's distribution timeline directly relevant to anyone whose care depends on knowing their stage rather than their diagnosis.
Frequently Asked Questions
Should I ask my doctor for the pTau217 blood test at my next visit?
Ask for a comprehensive clinical evaluation first. The Alzheimer's Association guideline specifically advises against ordering a blood biomarker test before that evaluation, and the Roche clearance covers adults 55 and older who already have symptoms of cognitive decline.
What does an "intermediate" blood test result mean for me?
It means the test could not place you clearly on either side of the cutoff. Roche's labeling treats that as a signal to pursue PET imaging or a cerebrospinal fluid test rather than as a diagnosis or an all-clear.
Does a negative tau PET scan mean I do not have Alzheimer's disease?
No. The TAUKLARIFY label states that performance may be lower at earlier stages of the pathologic spectrum, and that a negative scan does not independently exclude tau pathology. Early-stage patients in particular can scan negative with disease present.
Is TAUKLARIFY useful for other forms of dementia?
Its safety and effectiveness are not established for non-Alzheimer's tauopathies. The approved use is evaluating adults with cognitive impairment for Alzheimer's disease specifically.
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