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TODAY'S TOPIC
Alzheimer's Disease Diagnosis
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| That word on the tip of your tongue that refuses to arrive, and the small worry that follows it. A new test addresses what comes next, and its limits matter as much as its promise. |
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CLAIM 01
“A blood test can now help diagnose Alzheimer's disease.”
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| VERDICT TRUTH |
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For years, confirming Alzheimer's biology usually meant an amyloid PET scan or testing cerebrospinal fluid collected through a lumbar puncture. In May 2025, the FDA cleared the Lumipulse G pTau217/β-Amyloid 1-42 Plasma Ratio, the first blood-based in vitro diagnostic cleared to aid in Alzheimer's diagnosis. It measures p-tau217 and beta-amyloid 1-42 in plasma and calculates their ratio. In the FDA review study, 91.7% of positive test results agreed with amyloid pathology found by PET or CSF testing, while 97.3% of negative results agreed with a negative PET or CSF result. It can reduce the need for more invasive testing, but it does not replace the rest of the diagnostic workup. |
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SEE WHAT THE TEST ACTUALLY MEASURES
The FDA explains the new blood test in plain language.
See who the test is for, what p-tau217 and beta-amyloid mean, and how the result fits with PET or spinal fluid testing.
Read the FDA explainer →
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THE RESEARCH
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CLAIM 02
“The Alzheimer's blood test can tell a healthy person whether dementia is coming.”
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| VERDICT MYTH |
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The test detects amyloid pathology. It does not predict the future course of dementia in a healthy person. The FDA clearance applies to adults age 55 and older who already have signs and symptoms of cognitive decline and are being evaluated in a specialized care setting. The FDA specifically says Lumipulse is not intended as a screening test or as a stand-alone diagnostic test. Results must be interpreted together with the patient's symptoms, cognitive assessment, medical history, and other clinical information. A biomarker result tells you about amyloid pathology now. It does not tell a symptom-free person when dementia will begin. |
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WHAT BLOOD TESTING CAN AND CANNOT TELL YOU
The NIH has a patient-friendly blood test guide.
It explains amyloid, p-tau, PET scans, spinal fluid testing, accuracy limits, and why testing healthy people is not recommended outside research.
Read the NIH blood test guide →
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THE RESEARCH
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CLAIM 03
“The Alzheimer's blood test is equally accurate in every setting.”
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| VERDICT IT'S COMPLICATED |
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Test performance changes with the population being tested and the clinical setting. Data presented at CTAD 2025 found that the FDA-cleared Lumipulse cutpoints produced about 95% diagnostic accuracy in a research cohort enriched for Alzheimer's risk, but about 77% in a real-world memory clinic cohort. That does not mean the test suddenly stopped working. It means the mix of patients, prevalence of Alzheimer's pathology, cutpoints, laboratory performance, and pre-test probability can change what a positive or negative result means. The same laboratory number can carry different weight in different clinical contexts. |
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IMPORTANT 2026 UPDATE
Some Lumipulse lots are under an FDA Class 2 recall.
FDA reports that affected lots may produce more positive or indeterminate results than expected and may show lower specificity. Laboratories were instructed to stop using the affected lots and review previous results where appropriate.
Check the FDA recall record →
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HOW SPECIALISTS SHOULD USE BLOOD BIOMARKERS
The Alzheimer's Association now has a clinical guideline.
It explains when a blood biomarker can be used as a triage or confirmatory test, and why results still need a full clinical evaluation.
Read the Alzheimer's Association guideline →
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WHERE THE EVIDENCE SPLITS
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THE BOTTOM LINE
The blood test is a real step forward.
It still works best as one part of a clinical diagnosis, not as a prediction machine or a stand-alone answer.
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Which verdict surprised you most?
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| One tap. It decides what we dig into next. | ||
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