Tauklarify Tau PET vs Alzheimer's Blood Tests in 2026: What Is Established and What Remains Uncertain for Adults With New Memory Symptoms

Tauklarify and the new Alzheimer's blood tests measure different things and answer different questions. Tauklarify is a PET imaging tracer that shows tau tangles in the brain, while the blood tests screen for amyloid-related pathology from a blood draw — both now play a role in evaluating adults with new memory symptoms, but neither stands alone. The FDA approved Tauklarify (florquinitau F 18, also known as MK-6240) on August 14, 2026, for adults with cognitive impairment being evaluated for Alzheimer's disease, specifically to detect tau neurofibrillary tangles through brain PET imaging, according to SNMMI. Ten days later, on August 24, 2026, the FDA cleared Roche's Elecsys pTau217 blood test, developed with Eli Lilly, for adults 55 and older with cognitive complaints, as reported by Psychiatric Times.

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What Tauklarify Actually Shows
What the Blood Test Adds
Blood Test or PET Scan — Which Comes First?
What This Means for Someone With New Memory Symptoms

What Tauklarify Actually Shows

Tauklarify is a radioactive tracer injected before a PET scan. It binds to tau neurofibrillary tangles, one of the two hallmark proteins (along with amyloid) tied to Alzheimer's disease, and lights them up on the scan so a specialist can see how much tau pathology is present and where. The FDA's approval covers adults already undergoing evaluation for Alzheimer's disease, not a general screening population. The label states that safety and effectiveness have not been established for other tauopathies — brain diseases involving tau buildup that aren't Alzheimer's — and that tau PET is meant to complement, not replace, amyloid PET in reaching a diagnosis, per SNMMI.

The approval rested on two blinded-read studies spanning three trials and more than 500 subjects. Study 1, with 279 subjects, showed readers agreed on a positive result 80-88% of the time; Study 2, with 338 subjects, showed 68-82% agreement, according to Applied Radiology. That range reflects how tau PET reads can vary somewhat between radiologists, which is part of why it's positioned as one piece of evidence rather than a sole deciding factor. Tauklarify is only the second FDA-approved tau PET tracer, following Lilly's Tauvid (flortaucipir F-18). As of the approval announcement, Lantheus had not detailed when or where the scan would become available, per SNMMI.

What the Blood Test Adds

The Elecsys pTau217 test measures a specific form of tau protein in a blood sample and reports one of three results: negative, intermediate, or positive. It's used to help a clinician rule amyloid pathology in or out for adults 55 and older with cognitive complaints, per Psychiatric Times. This isn't the first blood test of its kind.

The Alzheimer's Association counts Roche's pTau217 as the fourth FDA-cleared Alzheimer's blood test overall, and the second cleared within about a week, following earlier clearances for Lumipulse in May 2025 and Fujirebio in 2025, according to the Alzheimer's Association. Access is set to widen quickly. Labcorp and Quest Diagnostics plan to offer the test, with Quest's launch slated for the fourth quarter of 2026, which puts a blood draw within reach of routine primary care visits rather than requiring a specialist referral up front, per BioBuzz/Reuters.

Blood Test or PET Scan — Which Comes First?

A blood test and a PET scan serve different points in the same evaluation, not competing paths to the same answer. The blood draw is accessible through primary care and can be ordered earlier, often as a way to decide whether more detailed imaging is warranted at all. A 2024 workgroup convened by the Global CEO Initiative on Alzheimer's set performance benchmarks for how these tests should be used: a triage blood test needs at least 90% sensitivity and 85% specificity, with any positive result confirmed by PET or a spinal fluid (CSF) test, according to Barcelona Beta.

A standalone confirmatory test, by contrast, needs roughly 90% accuracy on both measures, matching the accuracy of CSF testing. That same workgroup cautioned that a blood test's predictive value changes depending on how likely a given patient already is to have amyloid pathology before the test is run. A positive or negative result means something different in someone with classic memory symptoms than in someone with vague complaints, so the result needs interpretation in that clinical context rather than being read as a stand-alone yes-or-no diagnosis, per Barcelona Beta. In practice, this points toward a sequence: blood test first to gauge likelihood, PET or CSF testing to confirm when the result is positive or ambiguous.

What This Means for Someone With New Memory Symptoms

An adult noticing new or worsening memory problems has more starting points in late 2026 than in prior years. A few practical distinctions matter when discussing options with a clinician: None of these tests diagnoses Alzheimer's disease in isolation. Each narrows the picture, and the combination — patient history, cognitive testing, and biomarker results from blood and imaging — is what informs a diagnosis.

A blood test is typically ordered first and is available through primary care once Labcorp and Quest roll it out; it's intended for adults 55 and older with cognitive complaints.
Tauklarify and other tau PET scans are ordered for adults already being evaluated for Alzheimer's disease, usually after a primary workup, and require a nuclear medicine facility.
A positive blood test result generally calls for confirmation through PET or CSF testing rather than standing on its own.
Tau PET findings are meant to complement amyloid PET findings, not substitute for them, in reaching a diagnosis.