Tauklarify, a new PET imaging drug from Lantheus, won FDA approval in August 2026 for scanning the brains of adults with cognitive impairment for tau tangles, the protein clumps tied to Alzheimer's disease. In the same month, two blood tests for Alzheimer's-related amyloid pathology also cleared the FDA, giving doctors a faster, cheaper first step before anyone orders a brain scan. For someone newly diagnosed with mild cognitive impairment, or caring for someone who is, this changes the order of tests a neurologist might suggest, though not a single one of these tools decides an Alzheimer's diagnosis alone.
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 actually does
- How the new blood tests differ from a tau scan
- Why a blood test's lab numbers don't always hold up in practice
- Where this leaves someone with mild cognitive impairment
- Frequently Asked Questions
What Tauklarify actually does
Tauklarify (florquinitau F-18 injection, known in trials as MK-6240) is a radioactive tracer injected before a PET scan. It binds to tau neurofibrillary tangles, the twisted protein strands inside neurons that accumulate as Alzheimer's progresses, and lights them up on the scan. The FDA approved it on August 14, 2026, for use in adults with cognitive impairment who are being evaluated for Alzheimer's disease, according to Healio. It is only the second tau PET tracer ever approved by the FDA, following Eli Lilly's Tauvid (flortaucipir).
The approval rested on two blinded-read studies covering more than 500 subjects, with scan readers agreeing with the reference standard 80–88% of the time in one study and 68–82% of the time in the other, Healio reported. The drug's label is specific about its limits. Lantheus states that safety and effectiveness have not been established for evaluating tauopathies other than Alzheimer's disease, and that a single scan result, positive or negative, does not independently confirm or rule out tau pathology, Practical Neurology noted. A scan has to be read alongside other clinical findings, not treated as a standalone verdict.
How the new blood tests differ from a tau scan
Where Tauklarify images tau tangles directly inside the brain, the newly cleared blood tests measure a different marker: the ratio of phosphorylated tau 217 (pTau217) to amyloid-beta in a blood sample, which reflects amyloid plaque buildup rather than tau tangles themselves, per Healio and Practical Neurology's coverage. Amyloid and tau are both hallmarks of Alzheimer's, but they are separate biological targets, and a test built around one does not substitute for a test built around the other. Roche's Elecsys pTau217 test cleared the FDA on August 24, 2026, to help assess amyloid pathology in adults 55 and older with symptoms of cognitive decline.
It runs on Roche's existing cobas platform, already installed in more than 4,500 instruments across the U.S., and the FDA clearance explicitly describes it as an aid to diagnosis, not a stand-alone test, Practical Neurology reported. C2N Diagnostics' PrecivityAD2 cleared shortly after, around August 20–21, 2026, for symptomatic adults 40 and older. Its validation study of 1,142 participants, compared against amyloid PET or spinal fluid testing, reported a 97.6% positive predictive value and a 93.1% negative predictive value, according to Healio. Fujirebio's Lumipulse test, cleared in May 2025 as the first FDA-cleared Alzheimer's blood test, claimed 98% sensitivity and 91% specificity in its own 499-sample study, per MedTech Dive.
Why a blood test's lab numbers don't always hold up in practice
The sensitivity and specificity figures above come from controlled validation studies, and those numbers do not automatically carry over to a routine memory clinic. A real-world cohort presented at the Clinical Trials on Alzheimer's Disease (CTAD) conference in December 2025 tested Lumipulse using the FDA-cleared cutoff points and got only 23% specificity, translating to 77% overall accuracy. Using cutoffs calibrated to that specific clinic instead pushed accuracy to 91–96%, Practical Neurology reported. That gap matters for anyone reading a blood test result as a yes-or-no answer.
A test's published accuracy reflects the research population it was validated on, which tends to be more carefully selected for suspected Alzheimer's than the walk-in population at a general memory clinic. The same test, run in a broader clinical setting with different cutoffs, can produce far more false positives than its label numbers suggest. This is one reason none of these tests, blood-based or imaging-based, is positioned as sufficient on its own. A result still needs interpretation by a clinician weighing it against symptoms, other test results, and the patient's individual risk factors.
Where this leaves someone with mild cognitive impairment
Lantheus leadership has described tau PET as complementary to amyloid PET and blood testing, not a replacement for either, Healio and Practical Neurology reported. In practice, that points toward a sequence rather than a single decision: a blood test first, because it is far cheaper and easier to obtain, with imaging reserved for cases where the clinical picture still needs clarifying. Cost is a real factor in that sequence.
Amyloid PET scans run roughly $3,000 to $5,000 out of pocket, and Medicare patients generally still owe 20% coinsurance even after CMS lifted its one-scan-per-lifetime restriction in October 2023, according to Radiology Today. Blood tests are positioned explicitly as a cheaper first-line triage step to narrow down who actually needs a confirmatory scan like Tauklarify. For a patient or family member navigating a new MCI diagnosis, this means asking a neurologist directly which test comes first and why, rather than assuming a scan is the only path to an answer. It also means treating a blood test result as one input among several, not a final diagnosis, given how much the real-world performance of these tests can vary from their published validation numbers.
- Ask whether a pTau217 blood test (Roche Elecsys, C2N PrecivityAD2, or Fujirebio Lumipulse) is appropriate as a first step, based on age and symptoms.
- Ask what cutoff values the lab or clinic uses, since cleared cutoffs have performed inconsistently outside research cohorts.
- If a tau PET scan like Tauklarify is recommended, ask what it is expected to add beyond a blood test or amyloid PET already done.
- Check insurance coverage and expected coinsurance before scheduling any PET scan, given the $3,000–$5,000 typical cost.
Frequently Asked Questions
Is Tauklarify the same as a blood test for Alzheimer's?
No. Tauklarify is an injected PET imaging tracer that images tau tangles in the brain, while the blood tests measure a pTau217-to-amyloid ratio tied to amyloid plaques, a different marker in a different biological pathway.
Can a blood test alone diagnose Alzheimer's disease?
No. The FDA clearances for Roche's Elecsys pTau217 and similar tests describe them as aids to assessment, not stand-alone diagnostic tools, and a real-world study found their accuracy can drop sharply outside the cutoffs used in validation research.
Who is eligible for the PrecivityAD2 blood test?
C2N Diagnostics validated PrecivityAD2 for symptomatic adults age 40 and older, based on a 1,142-participant study compared against amyloid PET or spinal fluid results.
Does Medicare cover a Tauklarify PET scan?
Medicare generally covers amyloid-type PET scans since CMS removed its one-scan-per-lifetime limit in October 2023, but patients typically still owe 20% coinsurance on a scan that costs $3,000 to $5,000 out of pocket.
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