For the first time, a blood test rather than a brain scan or spinal tap can help determine whether a patient’s memory problems are tied to the biological hallmark of Alzheimer’s disease. The clearance marks a major shift toward earlier, less invasive detection, and it builds on a wider body of research showing that the same class of blood markers can flag Alzheimer’s-related brain changes years before a person shows any cognitive symptoms at all.
What The FDA Cleared, And When
On May 16, 2025, the U.S. Food and Drug Administration permitted marketing of the Lumipulse G pTau217/β-Amyloid 1-42 Plasma Ratio test, developed by Fujirebio Diagnostics, making it the first blood-based diagnostic test cleared in the country for aiding an Alzheimer’s diagnosis. The test became available nationwide through Labcorp in August 2025. It is cleared specifically for adults age 55 and older who are already showing signs of cognitive decline, such as memory loss or difficulty with everyday thinking tasks, and who are being evaluated for the cause.
The clearance followed an earlier, related test the FDA authorized in 2022 that measured a similar amyloid ratio but required more specialized lab processing. The newer version is intended to be simpler and more widely accessible through standard commercial laboratories, which is part of why its clearance is being treated as a bigger practical turning point than the earlier version.
How The Test Measures Amyloid Without A Scan
The test measures the ratio of two proteins in the blood: a specific phosphorylated form of tau and a form of beta-amyloid, the protein that clumps into the plaques found in the brains of people with Alzheimer’s disease. That ratio correlates closely with whether amyloid plaques are present, based on comparisons against PET brain imaging in clinical studies. Because it only requires a standard blood draw, the test is far less invasive and far cheaper than the two methods previously used to detect amyloid pathology in a living patient: a PET scan, which involves radioactive tracers, or a spinal tap to sample cerebrospinal fluid.
How Accurate The Test Has Been In Studies
In the clinical studies submitted to the FDA, 97% of people whose blood test came back positive for amyloid pathology also showed amyloid plaques on a follow-up PET scan, while 84% of people whose blood test came back negative also had a negative PET scan. Those figures place the blood test close to, though not identical with, the accuracy of PET imaging, which remains the more expensive and less accessible option for most patients. The gap on negative results is one reason the FDA cleared the test only as an aid to diagnosis rather than a standalone replacement for imaging, meaning a positive or ambiguous result can still prompt a doctor to order additional testing before finalizing a diagnosis.
What The Broader Research On Early Warning Signs Shows
The FDA clearance covers diagnostic use in people who already have symptoms, but a separate and substantial body of research has tracked the same class of biomarker, phosphorylated tau 217, in people with no cognitive symptoms at all. Long-running studies such as Sweden’s BioFINDER cohort have followed cognitively unimpaired participants for years, measuring plasma p-tau217 repeatedly over time, and found that rising levels tracked with subsequent cognitive decline and conversion to Alzheimer’s dementia well before symptoms became clinically apparent. Research published in the journal Brain found plasma p-tau217 outperformed related biomarkers at identifying early memory changes, reinforcing why the marker has become the leading candidate for detecting the disease’s biological onset years ahead of a diagnosis.
Alzheimer’s disease is now understood to involve a long preclinical phase in which amyloid plaques and tau tangles accumulate in the brain for years, sometimes over a decade, before memory or thinking problems become noticeable. Because p-tau217 tracks that underlying biology rather than symptoms directly, researchers have been able to detect rising levels in cognitively healthy study participants long before any clinical signs would prompt a doctor’s visit. That gap between biological onset and symptom onset is the basis for optimism that blood testing could eventually support much earlier intervention, though its current FDA clearance is limited to helping diagnose people who already have symptoms rather than screening the general public.
What Comes Next For Blood-Based Screening
The Alzheimer’s Association has described the clearance as a milestone that could shorten the diagnostic process for patients who currently wait weeks or months for a specialist referral and a PET scan or spinal tap. Researchers caution that broader use of blood tests to screen people with no symptoms raises separate questions, including how to counsel someone who tests positive for amyloid pathology but has no cognitive symptoms and may never develop Alzheimer’s disease during their lifetime. Clinical trials and screening protocols for asymptomatic use are still being developed, even as the diagnostic version of the test is already in use nationwide for symptomatic patients.
This article was produced with the assistance of AI and reviewed by Morning Overview editors.
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